1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * linux/mm/filemap.c
4 *
5 * Copyright (C) 1994-1999 Linus Torvalds
6 */
7
8 /*
9 * This file handles the generic file mmap semantics used by
10 * most "normal" filesystems (but you don't /have/ to use this:
11 * the NFS filesystem used to do this differently, for example)
12 */
13 #include <linux/export.h>
14 #include <linux/compiler.h>
15 #include <linux/dax.h>
16 #include <linux/fs.h>
17 #include <linux/sched/signal.h>
18 #include <linux/uaccess.h>
19 #include <linux/capability.h>
20 #include <linux/kernel_stat.h>
21 #include <linux/gfp.h>
22 #include <linux/mm.h>
23 #include <linux/swap.h>
24 #include <linux/mman.h>
25 #include <linux/pagemap.h>
26 #include <linux/file.h>
27 #include <linux/uio.h>
28 #include <linux/error-injection.h>
29 #include <linux/hash.h>
30 #include <linux/writeback.h>
31 #include <linux/backing-dev.h>
32 #include <linux/pagevec.h>
33 #include <linux/blkdev.h>
34 #include <linux/security.h>
35 #include <linux/cpuset.h>
36 #include <linux/hugetlb.h>
37 #include <linux/memcontrol.h>
38 #include <linux/cleancache.h>
39 #include <linux/shmem_fs.h>
40 #include <linux/rmap.h>
41 #include <linux/delayacct.h>
42 #include <linux/psi.h>
43 #include <linux/ramfs.h>
44 #include <linux/page_idle.h>
45 #include <asm/pgalloc.h>
46 #include <asm/tlbflush.h>
47 #include "internal.h"
48
49 #define CREATE_TRACE_POINTS
50 #include <trace/events/filemap.h>
51
52 /*
53 * FIXME: remove all knowledge of the buffer layer from the core VM
54 */
55 #include <linux/buffer_head.h> /* for try_to_free_buffers */
56
57 #include <asm/mman.h>
58
59 /*
60 * Shared mappings implemented 30.11.1994. It's not fully working yet,
61 * though.
62 *
63 * Shared mappings now work. 15.8.1995 Bruno.
64 *
65 * finished 'unifying' the page and buffer cache and SMP-threaded the
66 * page-cache, 21.05.1999, Ingo Molnar <mingo@redhat.com>
67 *
68 * SMP-threaded pagemap-LRU 1999, Andrea Arcangeli <andrea@suse.de>
69 */
70
71 /*
72 * Lock ordering:
73 *
74 * ->i_mmap_rwsem (truncate_pagecache)
75 * ->private_lock (__free_pte->__set_page_dirty_buffers)
76 * ->swap_lock (exclusive_swap_page, others)
77 * ->i_pages lock
78 *
79 * ->i_rwsem
80 * ->invalidate_lock (acquired by fs in truncate path)
81 * ->i_mmap_rwsem (truncate->unmap_mapping_range)
82 *
83 * ->mmap_lock
84 * ->i_mmap_rwsem
85 * ->page_table_lock or pte_lock (various, mainly in memory.c)
86 * ->i_pages lock (arch-dependent flush_dcache_mmap_lock)
87 *
88 * ->mmap_lock
89 * ->invalidate_lock (filemap_fault)
90 * ->lock_page (filemap_fault, access_process_vm)
91 *
92 * ->i_rwsem (generic_perform_write)
93 * ->mmap_lock (fault_in_pages_readable->do_page_fault)
94 *
95 * bdi->wb.list_lock
96 * sb_lock (fs/fs-writeback.c)
97 * ->i_pages lock (__sync_single_inode)
98 *
99 * ->i_mmap_rwsem
100 * ->anon_vma.lock (vma_adjust)
101 *
102 * ->anon_vma.lock
103 * ->page_table_lock or pte_lock (anon_vma_prepare and various)
104 *
105 * ->page_table_lock or pte_lock
106 * ->swap_lock (try_to_unmap_one)
107 * ->private_lock (try_to_unmap_one)
108 * ->i_pages lock (try_to_unmap_one)
109 * ->lruvec->lru_lock (follow_page->mark_page_accessed)
110 * ->lruvec->lru_lock (check_pte_range->isolate_lru_page)
111 * ->private_lock (page_remove_rmap->set_page_dirty)
112 * ->i_pages lock (page_remove_rmap->set_page_dirty)
113 * bdi.wb->list_lock (page_remove_rmap->set_page_dirty)
114 * ->inode->i_lock (page_remove_rmap->set_page_dirty)
115 * ->memcg->move_lock (page_remove_rmap->lock_page_memcg)
116 * bdi.wb->list_lock (zap_pte_range->set_page_dirty)
117 * ->inode->i_lock (zap_pte_range->set_page_dirty)
118 * ->private_lock (zap_pte_range->__set_page_dirty_buffers)
119 *
120 * ->i_mmap_rwsem
121 * ->tasklist_lock (memory_failure, collect_procs_ao)
122 */
123
page_cache_delete(struct address_space * mapping,struct page * page,void * shadow)124 static void page_cache_delete(struct address_space *mapping,
125 struct page *page, void *shadow)
126 {
127 XA_STATE(xas, &mapping->i_pages, page->index);
128 unsigned int nr = 1;
129
130 mapping_set_update(&xas, mapping);
131
132 /* hugetlb pages are represented by a single entry in the xarray */
133 if (!PageHuge(page)) {
134 xas_set_order(&xas, page->index, compound_order(page));
135 nr = compound_nr(page);
136 }
137
138 VM_BUG_ON_PAGE(!PageLocked(page), page);
139 VM_BUG_ON_PAGE(PageTail(page), page);
140 VM_BUG_ON_PAGE(nr != 1 && shadow, page);
141
142 xas_store(&xas, shadow);
143 xas_init_marks(&xas);
144
145 page->mapping = NULL;
146 /* Leave page->index set: truncation lookup relies upon it */
147 mapping->nrpages -= nr;
148 }
149
unaccount_page_cache_page(struct address_space * mapping,struct page * page)150 static void unaccount_page_cache_page(struct address_space *mapping,
151 struct page *page)
152 {
153 int nr;
154
155 /*
156 * if we're uptodate, flush out into the cleancache, otherwise
157 * invalidate any existing cleancache entries. We can't leave
158 * stale data around in the cleancache once our page is gone
159 */
160 if (PageUptodate(page) && PageMappedToDisk(page))
161 cleancache_put_page(page);
162 else
163 cleancache_invalidate_page(mapping, page);
164
165 VM_BUG_ON_PAGE(PageTail(page), page);
166 VM_BUG_ON_PAGE(page_mapped(page), page);
167 if (!IS_ENABLED(CONFIG_DEBUG_VM) && unlikely(page_mapped(page))) {
168 int mapcount;
169
170 pr_alert("BUG: Bad page cache in process %s pfn:%05lx\n",
171 current->comm, page_to_pfn(page));
172 dump_page(page, "still mapped when deleted");
173 dump_stack();
174 add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
175
176 mapcount = page_mapcount(page);
177 if (mapping_exiting(mapping) &&
178 page_count(page) >= mapcount + 2) {
179 /*
180 * All vmas have already been torn down, so it's
181 * a good bet that actually the page is unmapped,
182 * and we'd prefer not to leak it: if we're wrong,
183 * some other bad page check should catch it later.
184 */
185 page_mapcount_reset(page);
186 page_ref_sub(page, mapcount);
187 }
188 }
189
190 /* hugetlb pages do not participate in page cache accounting. */
191 if (PageHuge(page))
192 return;
193
194 nr = thp_nr_pages(page);
195
196 __mod_lruvec_page_state(page, NR_FILE_PAGES, -nr);
197 if (PageSwapBacked(page)) {
198 __mod_lruvec_page_state(page, NR_SHMEM, -nr);
199 if (PageTransHuge(page))
200 __mod_lruvec_page_state(page, NR_SHMEM_THPS, -nr);
201 } else if (PageTransHuge(page)) {
202 __mod_lruvec_page_state(page, NR_FILE_THPS, -nr);
203 filemap_nr_thps_dec(mapping);
204 }
205
206 /*
207 * At this point page must be either written or cleaned by
208 * truncate. Dirty page here signals a bug and loss of
209 * unwritten data.
210 *
211 * This fixes dirty accounting after removing the page entirely
212 * but leaves PageDirty set: it has no effect for truncated
213 * page and anyway will be cleared before returning page into
214 * buddy allocator.
215 */
216 if (WARN_ON_ONCE(PageDirty(page)))
217 account_page_cleaned(page, mapping, inode_to_wb(mapping->host));
218 }
219
220 /*
221 * Delete a page from the page cache and free it. Caller has to make
222 * sure the page is locked and that nobody else uses it - or that usage
223 * is safe. The caller must hold the i_pages lock.
224 */
__delete_from_page_cache(struct page * page,void * shadow)225 void __delete_from_page_cache(struct page *page, void *shadow)
226 {
227 struct address_space *mapping = page->mapping;
228
229 trace_mm_filemap_delete_from_page_cache(page);
230
231 unaccount_page_cache_page(mapping, page);
232 page_cache_delete(mapping, page, shadow);
233 }
234
page_cache_free_page(struct address_space * mapping,struct page * page)235 static void page_cache_free_page(struct address_space *mapping,
236 struct page *page)
237 {
238 void (*freepage)(struct page *);
239
240 freepage = mapping->a_ops->freepage;
241 if (freepage)
242 freepage(page);
243
244 if (PageTransHuge(page) && !PageHuge(page)) {
245 page_ref_sub(page, thp_nr_pages(page));
246 VM_BUG_ON_PAGE(page_count(page) <= 0, page);
247 } else {
248 put_page(page);
249 }
250 }
251
252 /**
253 * delete_from_page_cache - delete page from page cache
254 * @page: the page which the kernel is trying to remove from page cache
255 *
256 * This must be called only on pages that have been verified to be in the page
257 * cache and locked. It will never put the page into the free list, the caller
258 * has a reference on the page.
259 */
delete_from_page_cache(struct page * page)260 void delete_from_page_cache(struct page *page)
261 {
262 struct address_space *mapping = page_mapping(page);
263
264 BUG_ON(!PageLocked(page));
265 xa_lock_irq(&mapping->i_pages);
266 __delete_from_page_cache(page, NULL);
267 xa_unlock_irq(&mapping->i_pages);
268
269 page_cache_free_page(mapping, page);
270 }
271 EXPORT_SYMBOL(delete_from_page_cache);
272
273 /*
274 * page_cache_delete_batch - delete several pages from page cache
275 * @mapping: the mapping to which pages belong
276 * @pvec: pagevec with pages to delete
277 *
278 * The function walks over mapping->i_pages and removes pages passed in @pvec
279 * from the mapping. The function expects @pvec to be sorted by page index
280 * and is optimised for it to be dense.
281 * It tolerates holes in @pvec (mapping entries at those indices are not
282 * modified). The function expects only THP head pages to be present in the
283 * @pvec.
284 *
285 * The function expects the i_pages lock to be held.
286 */
page_cache_delete_batch(struct address_space * mapping,struct pagevec * pvec)287 static void page_cache_delete_batch(struct address_space *mapping,
288 struct pagevec *pvec)
289 {
290 XA_STATE(xas, &mapping->i_pages, pvec->pages[0]->index);
291 int total_pages = 0;
292 int i = 0;
293 struct page *page;
294
295 mapping_set_update(&xas, mapping);
296 xas_for_each(&xas, page, ULONG_MAX) {
297 if (i >= pagevec_count(pvec))
298 break;
299
300 /* A swap/dax/shadow entry got inserted? Skip it. */
301 if (xa_is_value(page))
302 continue;
303 /*
304 * A page got inserted in our range? Skip it. We have our
305 * pages locked so they are protected from being removed.
306 * If we see a page whose index is higher than ours, it
307 * means our page has been removed, which shouldn't be
308 * possible because we're holding the PageLock.
309 */
310 if (page != pvec->pages[i]) {
311 VM_BUG_ON_PAGE(page->index > pvec->pages[i]->index,
312 page);
313 continue;
314 }
315
316 WARN_ON_ONCE(!PageLocked(page));
317
318 if (page->index == xas.xa_index)
319 page->mapping = NULL;
320 /* Leave page->index set: truncation lookup relies on it */
321
322 /*
323 * Move to the next page in the vector if this is a regular
324 * page or the index is of the last sub-page of this compound
325 * page.
326 */
327 if (page->index + compound_nr(page) - 1 == xas.xa_index)
328 i++;
329 xas_store(&xas, NULL);
330 total_pages++;
331 }
332 mapping->nrpages -= total_pages;
333 }
334
delete_from_page_cache_batch(struct address_space * mapping,struct pagevec * pvec)335 void delete_from_page_cache_batch(struct address_space *mapping,
336 struct pagevec *pvec)
337 {
338 int i;
339
340 if (!pagevec_count(pvec))
341 return;
342
343 xa_lock_irq(&mapping->i_pages);
344 for (i = 0; i < pagevec_count(pvec); i++) {
345 trace_mm_filemap_delete_from_page_cache(pvec->pages[i]);
346
347 unaccount_page_cache_page(mapping, pvec->pages[i]);
348 }
349 page_cache_delete_batch(mapping, pvec);
350 xa_unlock_irq(&mapping->i_pages);
351
352 for (i = 0; i < pagevec_count(pvec); i++)
353 page_cache_free_page(mapping, pvec->pages[i]);
354 }
355
filemap_check_errors(struct address_space * mapping)356 int filemap_check_errors(struct address_space *mapping)
357 {
358 int ret = 0;
359 /* Check for outstanding write errors */
360 if (test_bit(AS_ENOSPC, &mapping->flags) &&
361 test_and_clear_bit(AS_ENOSPC, &mapping->flags))
362 ret = -ENOSPC;
363 if (test_bit(AS_EIO, &mapping->flags) &&
364 test_and_clear_bit(AS_EIO, &mapping->flags))
365 ret = -EIO;
366 return ret;
367 }
368 EXPORT_SYMBOL(filemap_check_errors);
369
filemap_check_and_keep_errors(struct address_space * mapping)370 static int filemap_check_and_keep_errors(struct address_space *mapping)
371 {
372 /* Check for outstanding write errors */
373 if (test_bit(AS_EIO, &mapping->flags))
374 return -EIO;
375 if (test_bit(AS_ENOSPC, &mapping->flags))
376 return -ENOSPC;
377 return 0;
378 }
379
380 /**
381 * filemap_fdatawrite_wbc - start writeback on mapping dirty pages in range
382 * @mapping: address space structure to write
383 * @wbc: the writeback_control controlling the writeout
384 *
385 * Call writepages on the mapping using the provided wbc to control the
386 * writeout.
387 *
388 * Return: %0 on success, negative error code otherwise.
389 */
filemap_fdatawrite_wbc(struct address_space * mapping,struct writeback_control * wbc)390 int filemap_fdatawrite_wbc(struct address_space *mapping,
391 struct writeback_control *wbc)
392 {
393 int ret;
394
395 if (!mapping_can_writeback(mapping) ||
396 !mapping_tagged(mapping, PAGECACHE_TAG_DIRTY))
397 return 0;
398
399 wbc_attach_fdatawrite_inode(wbc, mapping->host);
400 ret = do_writepages(mapping, wbc);
401 wbc_detach_inode(wbc);
402 return ret;
403 }
404 EXPORT_SYMBOL(filemap_fdatawrite_wbc);
405
406 /**
407 * __filemap_fdatawrite_range - start writeback on mapping dirty pages in range
408 * @mapping: address space structure to write
409 * @start: offset in bytes where the range starts
410 * @end: offset in bytes where the range ends (inclusive)
411 * @sync_mode: enable synchronous operation
412 *
413 * Start writeback against all of a mapping's dirty pages that lie
414 * within the byte offsets <start, end> inclusive.
415 *
416 * If sync_mode is WB_SYNC_ALL then this is a "data integrity" operation, as
417 * opposed to a regular memory cleansing writeback. The difference between
418 * these two operations is that if a dirty page/buffer is encountered, it must
419 * be waited upon, and not just skipped over.
420 *
421 * Return: %0 on success, negative error code otherwise.
422 */
__filemap_fdatawrite_range(struct address_space * mapping,loff_t start,loff_t end,int sync_mode)423 int __filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
424 loff_t end, int sync_mode)
425 {
426 struct writeback_control wbc = {
427 .sync_mode = sync_mode,
428 .nr_to_write = LONG_MAX,
429 .range_start = start,
430 .range_end = end,
431 };
432
433 return filemap_fdatawrite_wbc(mapping, &wbc);
434 }
435
__filemap_fdatawrite(struct address_space * mapping,int sync_mode)436 static inline int __filemap_fdatawrite(struct address_space *mapping,
437 int sync_mode)
438 {
439 return __filemap_fdatawrite_range(mapping, 0, LLONG_MAX, sync_mode);
440 }
441
filemap_fdatawrite(struct address_space * mapping)442 int filemap_fdatawrite(struct address_space *mapping)
443 {
444 return __filemap_fdatawrite(mapping, WB_SYNC_ALL);
445 }
446 EXPORT_SYMBOL(filemap_fdatawrite);
447
filemap_fdatawrite_range(struct address_space * mapping,loff_t start,loff_t end)448 int filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
449 loff_t end)
450 {
451 return __filemap_fdatawrite_range(mapping, start, end, WB_SYNC_ALL);
452 }
453 EXPORT_SYMBOL(filemap_fdatawrite_range);
454
455 /**
456 * filemap_flush - mostly a non-blocking flush
457 * @mapping: target address_space
458 *
459 * This is a mostly non-blocking flush. Not suitable for data-integrity
460 * purposes - I/O may not be started against all dirty pages.
461 *
462 * Return: %0 on success, negative error code otherwise.
463 */
filemap_flush(struct address_space * mapping)464 int filemap_flush(struct address_space *mapping)
465 {
466 return __filemap_fdatawrite(mapping, WB_SYNC_NONE);
467 }
468 EXPORT_SYMBOL(filemap_flush);
469
470 /**
471 * filemap_range_has_page - check if a page exists in range.
472 * @mapping: address space within which to check
473 * @start_byte: offset in bytes where the range starts
474 * @end_byte: offset in bytes where the range ends (inclusive)
475 *
476 * Find at least one page in the range supplied, usually used to check if
477 * direct writing in this range will trigger a writeback.
478 *
479 * Return: %true if at least one page exists in the specified range,
480 * %false otherwise.
481 */
filemap_range_has_page(struct address_space * mapping,loff_t start_byte,loff_t end_byte)482 bool filemap_range_has_page(struct address_space *mapping,
483 loff_t start_byte, loff_t end_byte)
484 {
485 struct page *page;
486 XA_STATE(xas, &mapping->i_pages, start_byte >> PAGE_SHIFT);
487 pgoff_t max = end_byte >> PAGE_SHIFT;
488
489 if (end_byte < start_byte)
490 return false;
491
492 rcu_read_lock();
493 for (;;) {
494 page = xas_find(&xas, max);
495 if (xas_retry(&xas, page))
496 continue;
497 /* Shadow entries don't count */
498 if (xa_is_value(page))
499 continue;
500 /*
501 * We don't need to try to pin this page; we're about to
502 * release the RCU lock anyway. It is enough to know that
503 * there was a page here recently.
504 */
505 break;
506 }
507 rcu_read_unlock();
508
509 return page != NULL;
510 }
511 EXPORT_SYMBOL(filemap_range_has_page);
512
__filemap_fdatawait_range(struct address_space * mapping,loff_t start_byte,loff_t end_byte)513 static void __filemap_fdatawait_range(struct address_space *mapping,
514 loff_t start_byte, loff_t end_byte)
515 {
516 pgoff_t index = start_byte >> PAGE_SHIFT;
517 pgoff_t end = end_byte >> PAGE_SHIFT;
518 struct pagevec pvec;
519 int nr_pages;
520
521 if (end_byte < start_byte)
522 return;
523
524 pagevec_init(&pvec);
525 while (index <= end) {
526 unsigned i;
527
528 nr_pages = pagevec_lookup_range_tag(&pvec, mapping, &index,
529 end, PAGECACHE_TAG_WRITEBACK);
530 if (!nr_pages)
531 break;
532
533 for (i = 0; i < nr_pages; i++) {
534 struct page *page = pvec.pages[i];
535
536 wait_on_page_writeback(page);
537 ClearPageError(page);
538 }
539 pagevec_release(&pvec);
540 cond_resched();
541 }
542 }
543
544 /**
545 * filemap_fdatawait_range - wait for writeback to complete
546 * @mapping: address space structure to wait for
547 * @start_byte: offset in bytes where the range starts
548 * @end_byte: offset in bytes where the range ends (inclusive)
549 *
550 * Walk the list of under-writeback pages of the given address space
551 * in the given range and wait for all of them. Check error status of
552 * the address space and return it.
553 *
554 * Since the error status of the address space is cleared by this function,
555 * callers are responsible for checking the return value and handling and/or
556 * reporting the error.
557 *
558 * Return: error status of the address space.
559 */
filemap_fdatawait_range(struct address_space * mapping,loff_t start_byte,loff_t end_byte)560 int filemap_fdatawait_range(struct address_space *mapping, loff_t start_byte,
561 loff_t end_byte)
562 {
563 __filemap_fdatawait_range(mapping, start_byte, end_byte);
564 return filemap_check_errors(mapping);
565 }
566 EXPORT_SYMBOL(filemap_fdatawait_range);
567
568 /**
569 * filemap_fdatawait_range_keep_errors - wait for writeback to complete
570 * @mapping: address space structure to wait for
571 * @start_byte: offset in bytes where the range starts
572 * @end_byte: offset in bytes where the range ends (inclusive)
573 *
574 * Walk the list of under-writeback pages of the given address space in the
575 * given range and wait for all of them. Unlike filemap_fdatawait_range(),
576 * this function does not clear error status of the address space.
577 *
578 * Use this function if callers don't handle errors themselves. Expected
579 * call sites are system-wide / filesystem-wide data flushers: e.g. sync(2),
580 * fsfreeze(8)
581 */
filemap_fdatawait_range_keep_errors(struct address_space * mapping,loff_t start_byte,loff_t end_byte)582 int filemap_fdatawait_range_keep_errors(struct address_space *mapping,
583 loff_t start_byte, loff_t end_byte)
584 {
585 __filemap_fdatawait_range(mapping, start_byte, end_byte);
586 return filemap_check_and_keep_errors(mapping);
587 }
588 EXPORT_SYMBOL(filemap_fdatawait_range_keep_errors);
589
590 /**
591 * file_fdatawait_range - wait for writeback to complete
592 * @file: file pointing to address space structure to wait for
593 * @start_byte: offset in bytes where the range starts
594 * @end_byte: offset in bytes where the range ends (inclusive)
595 *
596 * Walk the list of under-writeback pages of the address space that file
597 * refers to, in the given range and wait for all of them. Check error
598 * status of the address space vs. the file->f_wb_err cursor and return it.
599 *
600 * Since the error status of the file is advanced by this function,
601 * callers are responsible for checking the return value and handling and/or
602 * reporting the error.
603 *
604 * Return: error status of the address space vs. the file->f_wb_err cursor.
605 */
file_fdatawait_range(struct file * file,loff_t start_byte,loff_t end_byte)606 int file_fdatawait_range(struct file *file, loff_t start_byte, loff_t end_byte)
607 {
608 struct address_space *mapping = file->f_mapping;
609
610 __filemap_fdatawait_range(mapping, start_byte, end_byte);
611 return file_check_and_advance_wb_err(file);
612 }
613 EXPORT_SYMBOL(file_fdatawait_range);
614
615 /**
616 * filemap_fdatawait_keep_errors - wait for writeback without clearing errors
617 * @mapping: address space structure to wait for
618 *
619 * Walk the list of under-writeback pages of the given address space
620 * and wait for all of them. Unlike filemap_fdatawait(), this function
621 * does not clear error status of the address space.
622 *
623 * Use this function if callers don't handle errors themselves. Expected
624 * call sites are system-wide / filesystem-wide data flushers: e.g. sync(2),
625 * fsfreeze(8)
626 *
627 * Return: error status of the address space.
628 */
filemap_fdatawait_keep_errors(struct address_space * mapping)629 int filemap_fdatawait_keep_errors(struct address_space *mapping)
630 {
631 __filemap_fdatawait_range(mapping, 0, LLONG_MAX);
632 return filemap_check_and_keep_errors(mapping);
633 }
634 EXPORT_SYMBOL(filemap_fdatawait_keep_errors);
635
636 /* Returns true if writeback might be needed or already in progress. */
mapping_needs_writeback(struct address_space * mapping)637 static bool mapping_needs_writeback(struct address_space *mapping)
638 {
639 return mapping->nrpages;
640 }
641
642 /**
643 * filemap_range_needs_writeback - check if range potentially needs writeback
644 * @mapping: address space within which to check
645 * @start_byte: offset in bytes where the range starts
646 * @end_byte: offset in bytes where the range ends (inclusive)
647 *
648 * Find at least one page in the range supplied, usually used to check if
649 * direct writing in this range will trigger a writeback. Used by O_DIRECT
650 * read/write with IOCB_NOWAIT, to see if the caller needs to do
651 * filemap_write_and_wait_range() before proceeding.
652 *
653 * Return: %true if the caller should do filemap_write_and_wait_range() before
654 * doing O_DIRECT to a page in this range, %false otherwise.
655 */
filemap_range_needs_writeback(struct address_space * mapping,loff_t start_byte,loff_t end_byte)656 bool filemap_range_needs_writeback(struct address_space *mapping,
657 loff_t start_byte, loff_t end_byte)
658 {
659 XA_STATE(xas, &mapping->i_pages, start_byte >> PAGE_SHIFT);
660 pgoff_t max = end_byte >> PAGE_SHIFT;
661 struct page *page;
662
663 if (!mapping_needs_writeback(mapping))
664 return false;
665 if (!mapping_tagged(mapping, PAGECACHE_TAG_DIRTY) &&
666 !mapping_tagged(mapping, PAGECACHE_TAG_WRITEBACK))
667 return false;
668 if (end_byte < start_byte)
669 return false;
670
671 rcu_read_lock();
672 xas_for_each(&xas, page, max) {
673 if (xas_retry(&xas, page))
674 continue;
675 if (xa_is_value(page))
676 continue;
677 if (PageDirty(page) || PageLocked(page) || PageWriteback(page))
678 break;
679 }
680 rcu_read_unlock();
681 return page != NULL;
682 }
683 EXPORT_SYMBOL_GPL(filemap_range_needs_writeback);
684
685 /**
686 * filemap_write_and_wait_range - write out & wait on a file range
687 * @mapping: the address_space for the pages
688 * @lstart: offset in bytes where the range starts
689 * @lend: offset in bytes where the range ends (inclusive)
690 *
691 * Write out and wait upon file offsets lstart->lend, inclusive.
692 *
693 * Note that @lend is inclusive (describes the last byte to be written) so
694 * that this function can be used to write to the very end-of-file (end = -1).
695 *
696 * Return: error status of the address space.
697 */
filemap_write_and_wait_range(struct address_space * mapping,loff_t lstart,loff_t lend)698 int filemap_write_and_wait_range(struct address_space *mapping,
699 loff_t lstart, loff_t lend)
700 {
701 int err = 0;
702
703 if (mapping_needs_writeback(mapping)) {
704 err = __filemap_fdatawrite_range(mapping, lstart, lend,
705 WB_SYNC_ALL);
706 /*
707 * Even if the above returned error, the pages may be
708 * written partially (e.g. -ENOSPC), so we wait for it.
709 * But the -EIO is special case, it may indicate the worst
710 * thing (e.g. bug) happened, so we avoid waiting for it.
711 */
712 if (err != -EIO) {
713 int err2 = filemap_fdatawait_range(mapping,
714 lstart, lend);
715 if (!err)
716 err = err2;
717 } else {
718 /* Clear any previously stored errors */
719 filemap_check_errors(mapping);
720 }
721 } else {
722 err = filemap_check_errors(mapping);
723 }
724 return err;
725 }
726 EXPORT_SYMBOL(filemap_write_and_wait_range);
727
__filemap_set_wb_err(struct address_space * mapping,int err)728 void __filemap_set_wb_err(struct address_space *mapping, int err)
729 {
730 errseq_t eseq = errseq_set(&mapping->wb_err, err);
731
732 trace_filemap_set_wb_err(mapping, eseq);
733 }
734 EXPORT_SYMBOL(__filemap_set_wb_err);
735
736 /**
737 * file_check_and_advance_wb_err - report wb error (if any) that was previously
738 * and advance wb_err to current one
739 * @file: struct file on which the error is being reported
740 *
741 * When userland calls fsync (or something like nfsd does the equivalent), we
742 * want to report any writeback errors that occurred since the last fsync (or
743 * since the file was opened if there haven't been any).
744 *
745 * Grab the wb_err from the mapping. If it matches what we have in the file,
746 * then just quickly return 0. The file is all caught up.
747 *
748 * If it doesn't match, then take the mapping value, set the "seen" flag in
749 * it and try to swap it into place. If it works, or another task beat us
750 * to it with the new value, then update the f_wb_err and return the error
751 * portion. The error at this point must be reported via proper channels
752 * (a'la fsync, or NFS COMMIT operation, etc.).
753 *
754 * While we handle mapping->wb_err with atomic operations, the f_wb_err
755 * value is protected by the f_lock since we must ensure that it reflects
756 * the latest value swapped in for this file descriptor.
757 *
758 * Return: %0 on success, negative error code otherwise.
759 */
file_check_and_advance_wb_err(struct file * file)760 int file_check_and_advance_wb_err(struct file *file)
761 {
762 int err = 0;
763 errseq_t old = READ_ONCE(file->f_wb_err);
764 struct address_space *mapping = file->f_mapping;
765
766 /* Locklessly handle the common case where nothing has changed */
767 if (errseq_check(&mapping->wb_err, old)) {
768 /* Something changed, must use slow path */
769 spin_lock(&file->f_lock);
770 old = file->f_wb_err;
771 err = errseq_check_and_advance(&mapping->wb_err,
772 &file->f_wb_err);
773 trace_file_check_and_advance_wb_err(file, old);
774 spin_unlock(&file->f_lock);
775 }
776
777 /*
778 * We're mostly using this function as a drop in replacement for
779 * filemap_check_errors. Clear AS_EIO/AS_ENOSPC to emulate the effect
780 * that the legacy code would have had on these flags.
781 */
782 clear_bit(AS_EIO, &mapping->flags);
783 clear_bit(AS_ENOSPC, &mapping->flags);
784 return err;
785 }
786 EXPORT_SYMBOL(file_check_and_advance_wb_err);
787
788 /**
789 * file_write_and_wait_range - write out & wait on a file range
790 * @file: file pointing to address_space with pages
791 * @lstart: offset in bytes where the range starts
792 * @lend: offset in bytes where the range ends (inclusive)
793 *
794 * Write out and wait upon file offsets lstart->lend, inclusive.
795 *
796 * Note that @lend is inclusive (describes the last byte to be written) so
797 * that this function can be used to write to the very end-of-file (end = -1).
798 *
799 * After writing out and waiting on the data, we check and advance the
800 * f_wb_err cursor to the latest value, and return any errors detected there.
801 *
802 * Return: %0 on success, negative error code otherwise.
803 */
file_write_and_wait_range(struct file * file,loff_t lstart,loff_t lend)804 int file_write_and_wait_range(struct file *file, loff_t lstart, loff_t lend)
805 {
806 int err = 0, err2;
807 struct address_space *mapping = file->f_mapping;
808
809 if (mapping_needs_writeback(mapping)) {
810 err = __filemap_fdatawrite_range(mapping, lstart, lend,
811 WB_SYNC_ALL);
812 /* See comment of filemap_write_and_wait() */
813 if (err != -EIO)
814 __filemap_fdatawait_range(mapping, lstart, lend);
815 }
816 err2 = file_check_and_advance_wb_err(file);
817 if (!err)
818 err = err2;
819 return err;
820 }
821 EXPORT_SYMBOL(file_write_and_wait_range);
822
823 /**
824 * replace_page_cache_page - replace a pagecache page with a new one
825 * @old: page to be replaced
826 * @new: page to replace with
827 *
828 * This function replaces a page in the pagecache with a new one. On
829 * success it acquires the pagecache reference for the new page and
830 * drops it for the old page. Both the old and new pages must be
831 * locked. This function does not add the new page to the LRU, the
832 * caller must do that.
833 *
834 * The remove + add is atomic. This function cannot fail.
835 */
replace_page_cache_page(struct page * old,struct page * new)836 void replace_page_cache_page(struct page *old, struct page *new)
837 {
838 struct address_space *mapping = old->mapping;
839 void (*freepage)(struct page *) = mapping->a_ops->freepage;
840 pgoff_t offset = old->index;
841 XA_STATE(xas, &mapping->i_pages, offset);
842
843 VM_BUG_ON_PAGE(!PageLocked(old), old);
844 VM_BUG_ON_PAGE(!PageLocked(new), new);
845 VM_BUG_ON_PAGE(new->mapping, new);
846
847 get_page(new);
848 new->mapping = mapping;
849 new->index = offset;
850
851 mem_cgroup_migrate(old, new);
852
853 xas_lock_irq(&xas);
854 xas_store(&xas, new);
855
856 old->mapping = NULL;
857 /* hugetlb pages do not participate in page cache accounting. */
858 if (!PageHuge(old))
859 __dec_lruvec_page_state(old, NR_FILE_PAGES);
860 if (!PageHuge(new))
861 __inc_lruvec_page_state(new, NR_FILE_PAGES);
862 if (PageSwapBacked(old))
863 __dec_lruvec_page_state(old, NR_SHMEM);
864 if (PageSwapBacked(new))
865 __inc_lruvec_page_state(new, NR_SHMEM);
866 xas_unlock_irq(&xas);
867 if (freepage)
868 freepage(old);
869 put_page(old);
870 }
871 EXPORT_SYMBOL_GPL(replace_page_cache_page);
872
__add_to_page_cache_locked(struct page * page,struct address_space * mapping,pgoff_t offset,gfp_t gfp,void ** shadowp)873 noinline int __add_to_page_cache_locked(struct page *page,
874 struct address_space *mapping,
875 pgoff_t offset, gfp_t gfp,
876 void **shadowp)
877 {
878 XA_STATE(xas, &mapping->i_pages, offset);
879 int huge = PageHuge(page);
880 int error;
881 bool charged = false;
882
883 VM_BUG_ON_PAGE(!PageLocked(page), page);
884 VM_BUG_ON_PAGE(PageSwapBacked(page), page);
885 mapping_set_update(&xas, mapping);
886
887 get_page(page);
888 page->mapping = mapping;
889 page->index = offset;
890
891 if (!huge) {
892 error = mem_cgroup_charge(page, NULL, gfp);
893 if (error)
894 goto error;
895 charged = true;
896 }
897
898 gfp &= GFP_RECLAIM_MASK;
899
900 do {
901 unsigned int order = xa_get_order(xas.xa, xas.xa_index);
902 void *entry, *old = NULL;
903
904 if (order > thp_order(page))
905 xas_split_alloc(&xas, xa_load(xas.xa, xas.xa_index),
906 order, gfp);
907 xas_lock_irq(&xas);
908 xas_for_each_conflict(&xas, entry) {
909 old = entry;
910 if (!xa_is_value(entry)) {
911 xas_set_err(&xas, -EEXIST);
912 goto unlock;
913 }
914 }
915
916 if (old) {
917 if (shadowp)
918 *shadowp = old;
919 /* entry may have been split before we acquired lock */
920 order = xa_get_order(xas.xa, xas.xa_index);
921 if (order > thp_order(page)) {
922 xas_split(&xas, old, order);
923 xas_reset(&xas);
924 }
925 }
926
927 xas_store(&xas, page);
928 if (xas_error(&xas))
929 goto unlock;
930
931 mapping->nrpages++;
932
933 /* hugetlb pages do not participate in page cache accounting */
934 if (!huge)
935 __inc_lruvec_page_state(page, NR_FILE_PAGES);
936 unlock:
937 xas_unlock_irq(&xas);
938 } while (xas_nomem(&xas, gfp));
939
940 if (xas_error(&xas)) {
941 error = xas_error(&xas);
942 if (charged)
943 mem_cgroup_uncharge(page);
944 goto error;
945 }
946
947 trace_mm_filemap_add_to_page_cache(page);
948 return 0;
949 error:
950 page->mapping = NULL;
951 /* Leave page->index set: truncation relies upon it */
952 put_page(page);
953 return error;
954 }
955 ALLOW_ERROR_INJECTION(__add_to_page_cache_locked, ERRNO);
956
957 /**
958 * add_to_page_cache_locked - add a locked page to the pagecache
959 * @page: page to add
960 * @mapping: the page's address_space
961 * @offset: page index
962 * @gfp_mask: page allocation mode
963 *
964 * This function is used to add a page to the pagecache. It must be locked.
965 * This function does not add the page to the LRU. The caller must do that.
966 *
967 * Return: %0 on success, negative error code otherwise.
968 */
add_to_page_cache_locked(struct page * page,struct address_space * mapping,pgoff_t offset,gfp_t gfp_mask)969 int add_to_page_cache_locked(struct page *page, struct address_space *mapping,
970 pgoff_t offset, gfp_t gfp_mask)
971 {
972 return __add_to_page_cache_locked(page, mapping, offset,
973 gfp_mask, NULL);
974 }
975 EXPORT_SYMBOL(add_to_page_cache_locked);
976
add_to_page_cache_lru(struct page * page,struct address_space * mapping,pgoff_t offset,gfp_t gfp_mask)977 int add_to_page_cache_lru(struct page *page, struct address_space *mapping,
978 pgoff_t offset, gfp_t gfp_mask)
979 {
980 void *shadow = NULL;
981 int ret;
982
983 __SetPageLocked(page);
984 ret = __add_to_page_cache_locked(page, mapping, offset,
985 gfp_mask, &shadow);
986 if (unlikely(ret))
987 __ClearPageLocked(page);
988 else {
989 /*
990 * The page might have been evicted from cache only
991 * recently, in which case it should be activated like
992 * any other repeatedly accessed page.
993 * The exception is pages getting rewritten; evicting other
994 * data from the working set, only to cache data that will
995 * get overwritten with something else, is a waste of memory.
996 */
997 WARN_ON_ONCE(PageActive(page));
998 if (!(gfp_mask & __GFP_WRITE) && shadow)
999 workingset_refault(page, shadow);
1000 lru_cache_add(page);
1001 }
1002 return ret;
1003 }
1004 EXPORT_SYMBOL_GPL(add_to_page_cache_lru);
1005
1006 #ifdef CONFIG_NUMA
__page_cache_alloc(gfp_t gfp)1007 struct page *__page_cache_alloc(gfp_t gfp)
1008 {
1009 int n;
1010 struct page *page;
1011
1012 if (cpuset_do_page_mem_spread()) {
1013 unsigned int cpuset_mems_cookie;
1014 do {
1015 cpuset_mems_cookie = read_mems_allowed_begin();
1016 n = cpuset_mem_spread_node();
1017 page = __alloc_pages_node(n, gfp, 0);
1018 } while (!page && read_mems_allowed_retry(cpuset_mems_cookie));
1019
1020 return page;
1021 }
1022 return alloc_pages(gfp, 0);
1023 }
1024 EXPORT_SYMBOL(__page_cache_alloc);
1025 #endif
1026
1027 /*
1028 * filemap_invalidate_lock_two - lock invalidate_lock for two mappings
1029 *
1030 * Lock exclusively invalidate_lock of any passed mapping that is not NULL.
1031 *
1032 * @mapping1: the first mapping to lock
1033 * @mapping2: the second mapping to lock
1034 */
filemap_invalidate_lock_two(struct address_space * mapping1,struct address_space * mapping2)1035 void filemap_invalidate_lock_two(struct address_space *mapping1,
1036 struct address_space *mapping2)
1037 {
1038 if (mapping1 > mapping2)
1039 swap(mapping1, mapping2);
1040 if (mapping1)
1041 down_write(&mapping1->invalidate_lock);
1042 if (mapping2 && mapping1 != mapping2)
1043 down_write_nested(&mapping2->invalidate_lock, 1);
1044 }
1045 EXPORT_SYMBOL(filemap_invalidate_lock_two);
1046
1047 /*
1048 * filemap_invalidate_unlock_two - unlock invalidate_lock for two mappings
1049 *
1050 * Unlock exclusive invalidate_lock of any passed mapping that is not NULL.
1051 *
1052 * @mapping1: the first mapping to unlock
1053 * @mapping2: the second mapping to unlock
1054 */
filemap_invalidate_unlock_two(struct address_space * mapping1,struct address_space * mapping2)1055 void filemap_invalidate_unlock_two(struct address_space *mapping1,
1056 struct address_space *mapping2)
1057 {
1058 if (mapping1)
1059 up_write(&mapping1->invalidate_lock);
1060 if (mapping2 && mapping1 != mapping2)
1061 up_write(&mapping2->invalidate_lock);
1062 }
1063 EXPORT_SYMBOL(filemap_invalidate_unlock_two);
1064
1065 /*
1066 * In order to wait for pages to become available there must be
1067 * waitqueues associated with pages. By using a hash table of
1068 * waitqueues where the bucket discipline is to maintain all
1069 * waiters on the same queue and wake all when any of the pages
1070 * become available, and for the woken contexts to check to be
1071 * sure the appropriate page became available, this saves space
1072 * at a cost of "thundering herd" phenomena during rare hash
1073 * collisions.
1074 */
1075 #define PAGE_WAIT_TABLE_BITS 8
1076 #define PAGE_WAIT_TABLE_SIZE (1 << PAGE_WAIT_TABLE_BITS)
1077 static wait_queue_head_t page_wait_table[PAGE_WAIT_TABLE_SIZE] __cacheline_aligned;
1078
page_waitqueue(struct page * page)1079 static wait_queue_head_t *page_waitqueue(struct page *page)
1080 {
1081 return &page_wait_table[hash_ptr(page, PAGE_WAIT_TABLE_BITS)];
1082 }
1083
pagecache_init(void)1084 void __init pagecache_init(void)
1085 {
1086 int i;
1087
1088 for (i = 0; i < PAGE_WAIT_TABLE_SIZE; i++)
1089 init_waitqueue_head(&page_wait_table[i]);
1090
1091 page_writeback_init();
1092 }
1093
1094 /*
1095 * The page wait code treats the "wait->flags" somewhat unusually, because
1096 * we have multiple different kinds of waits, not just the usual "exclusive"
1097 * one.
1098 *
1099 * We have:
1100 *
1101 * (a) no special bits set:
1102 *
1103 * We're just waiting for the bit to be released, and when a waker
1104 * calls the wakeup function, we set WQ_FLAG_WOKEN and wake it up,
1105 * and remove it from the wait queue.
1106 *
1107 * Simple and straightforward.
1108 *
1109 * (b) WQ_FLAG_EXCLUSIVE:
1110 *
1111 * The waiter is waiting to get the lock, and only one waiter should
1112 * be woken up to avoid any thundering herd behavior. We'll set the
1113 * WQ_FLAG_WOKEN bit, wake it up, and remove it from the wait queue.
1114 *
1115 * This is the traditional exclusive wait.
1116 *
1117 * (c) WQ_FLAG_EXCLUSIVE | WQ_FLAG_CUSTOM:
1118 *
1119 * The waiter is waiting to get the bit, and additionally wants the
1120 * lock to be transferred to it for fair lock behavior. If the lock
1121 * cannot be taken, we stop walking the wait queue without waking
1122 * the waiter.
1123 *
1124 * This is the "fair lock handoff" case, and in addition to setting
1125 * WQ_FLAG_WOKEN, we set WQ_FLAG_DONE to let the waiter easily see
1126 * that it now has the lock.
1127 */
wake_page_function(wait_queue_entry_t * wait,unsigned mode,int sync,void * arg)1128 static int wake_page_function(wait_queue_entry_t *wait, unsigned mode, int sync, void *arg)
1129 {
1130 unsigned int flags;
1131 struct wait_page_key *key = arg;
1132 struct wait_page_queue *wait_page
1133 = container_of(wait, struct wait_page_queue, wait);
1134
1135 if (!wake_page_match(wait_page, key))
1136 return 0;
1137
1138 /*
1139 * If it's a lock handoff wait, we get the bit for it, and
1140 * stop walking (and do not wake it up) if we can't.
1141 */
1142 flags = wait->flags;
1143 if (flags & WQ_FLAG_EXCLUSIVE) {
1144 if (test_bit(key->bit_nr, &key->page->flags))
1145 return -1;
1146 if (flags & WQ_FLAG_CUSTOM) {
1147 if (test_and_set_bit(key->bit_nr, &key->page->flags))
1148 return -1;
1149 flags |= WQ_FLAG_DONE;
1150 }
1151 }
1152
1153 /*
1154 * We are holding the wait-queue lock, but the waiter that
1155 * is waiting for this will be checking the flags without
1156 * any locking.
1157 *
1158 * So update the flags atomically, and wake up the waiter
1159 * afterwards to avoid any races. This store-release pairs
1160 * with the load-acquire in wait_on_page_bit_common().
1161 */
1162 smp_store_release(&wait->flags, flags | WQ_FLAG_WOKEN);
1163 wake_up_state(wait->private, mode);
1164
1165 /*
1166 * Ok, we have successfully done what we're waiting for,
1167 * and we can unconditionally remove the wait entry.
1168 *
1169 * Note that this pairs with the "finish_wait()" in the
1170 * waiter, and has to be the absolute last thing we do.
1171 * After this list_del_init(&wait->entry) the wait entry
1172 * might be de-allocated and the process might even have
1173 * exited.
1174 */
1175 list_del_init_careful(&wait->entry);
1176 return (flags & WQ_FLAG_EXCLUSIVE) != 0;
1177 }
1178
wake_up_page_bit(struct page * page,int bit_nr)1179 static void wake_up_page_bit(struct page *page, int bit_nr)
1180 {
1181 wait_queue_head_t *q = page_waitqueue(page);
1182 struct wait_page_key key;
1183 unsigned long flags;
1184 wait_queue_entry_t bookmark;
1185
1186 key.page = page;
1187 key.bit_nr = bit_nr;
1188 key.page_match = 0;
1189
1190 bookmark.flags = 0;
1191 bookmark.private = NULL;
1192 bookmark.func = NULL;
1193 INIT_LIST_HEAD(&bookmark.entry);
1194
1195 spin_lock_irqsave(&q->lock, flags);
1196 __wake_up_locked_key_bookmark(q, TASK_NORMAL, &key, &bookmark);
1197
1198 while (bookmark.flags & WQ_FLAG_BOOKMARK) {
1199 /*
1200 * Take a breather from holding the lock,
1201 * allow pages that finish wake up asynchronously
1202 * to acquire the lock and remove themselves
1203 * from wait queue
1204 */
1205 spin_unlock_irqrestore(&q->lock, flags);
1206 cpu_relax();
1207 spin_lock_irqsave(&q->lock, flags);
1208 __wake_up_locked_key_bookmark(q, TASK_NORMAL, &key, &bookmark);
1209 }
1210
1211 /*
1212 * It is possible for other pages to have collided on the waitqueue
1213 * hash, so in that case check for a page match. That prevents a long-
1214 * term waiter
1215 *
1216 * It is still possible to miss a case here, when we woke page waiters
1217 * and removed them from the waitqueue, but there are still other
1218 * page waiters.
1219 */
1220 if (!waitqueue_active(q) || !key.page_match) {
1221 ClearPageWaiters(page);
1222 /*
1223 * It's possible to miss clearing Waiters here, when we woke
1224 * our page waiters, but the hashed waitqueue has waiters for
1225 * other pages on it.
1226 *
1227 * That's okay, it's a rare case. The next waker will clear it.
1228 */
1229 }
1230 spin_unlock_irqrestore(&q->lock, flags);
1231 }
1232
wake_up_page(struct page * page,int bit)1233 static void wake_up_page(struct page *page, int bit)
1234 {
1235 if (!PageWaiters(page))
1236 return;
1237 wake_up_page_bit(page, bit);
1238 }
1239
1240 /*
1241 * A choice of three behaviors for wait_on_page_bit_common():
1242 */
1243 enum behavior {
1244 EXCLUSIVE, /* Hold ref to page and take the bit when woken, like
1245 * __lock_page() waiting on then setting PG_locked.
1246 */
1247 SHARED, /* Hold ref to page and check the bit when woken, like
1248 * wait_on_page_writeback() waiting on PG_writeback.
1249 */
1250 DROP, /* Drop ref to page before wait, no check when woken,
1251 * like put_and_wait_on_page_locked() on PG_locked.
1252 */
1253 };
1254
1255 /*
1256 * Attempt to check (or get) the page bit, and mark us done
1257 * if successful.
1258 */
trylock_page_bit_common(struct page * page,int bit_nr,struct wait_queue_entry * wait)1259 static inline bool trylock_page_bit_common(struct page *page, int bit_nr,
1260 struct wait_queue_entry *wait)
1261 {
1262 if (wait->flags & WQ_FLAG_EXCLUSIVE) {
1263 if (test_and_set_bit(bit_nr, &page->flags))
1264 return false;
1265 } else if (test_bit(bit_nr, &page->flags))
1266 return false;
1267
1268 wait->flags |= WQ_FLAG_WOKEN | WQ_FLAG_DONE;
1269 return true;
1270 }
1271
1272 /* How many times do we accept lock stealing from under a waiter? */
1273 int sysctl_page_lock_unfairness = 5;
1274
wait_on_page_bit_common(wait_queue_head_t * q,struct page * page,int bit_nr,int state,enum behavior behavior)1275 static inline int wait_on_page_bit_common(wait_queue_head_t *q,
1276 struct page *page, int bit_nr, int state, enum behavior behavior)
1277 {
1278 int unfairness = sysctl_page_lock_unfairness;
1279 struct wait_page_queue wait_page;
1280 wait_queue_entry_t *wait = &wait_page.wait;
1281 bool thrashing = false;
1282 bool delayacct = false;
1283 unsigned long pflags;
1284
1285 if (bit_nr == PG_locked &&
1286 !PageUptodate(page) && PageWorkingset(page)) {
1287 if (!PageSwapBacked(page)) {
1288 delayacct_thrashing_start();
1289 delayacct = true;
1290 }
1291 psi_memstall_enter(&pflags);
1292 thrashing = true;
1293 }
1294
1295 init_wait(wait);
1296 wait->func = wake_page_function;
1297 wait_page.page = page;
1298 wait_page.bit_nr = bit_nr;
1299
1300 repeat:
1301 wait->flags = 0;
1302 if (behavior == EXCLUSIVE) {
1303 wait->flags = WQ_FLAG_EXCLUSIVE;
1304 if (--unfairness < 0)
1305 wait->flags |= WQ_FLAG_CUSTOM;
1306 }
1307
1308 /*
1309 * Do one last check whether we can get the
1310 * page bit synchronously.
1311 *
1312 * Do the SetPageWaiters() marking before that
1313 * to let any waker we _just_ missed know they
1314 * need to wake us up (otherwise they'll never
1315 * even go to the slow case that looks at the
1316 * page queue), and add ourselves to the wait
1317 * queue if we need to sleep.
1318 *
1319 * This part needs to be done under the queue
1320 * lock to avoid races.
1321 */
1322 spin_lock_irq(&q->lock);
1323 SetPageWaiters(page);
1324 if (!trylock_page_bit_common(page, bit_nr, wait))
1325 __add_wait_queue_entry_tail(q, wait);
1326 spin_unlock_irq(&q->lock);
1327
1328 /*
1329 * From now on, all the logic will be based on
1330 * the WQ_FLAG_WOKEN and WQ_FLAG_DONE flag, to
1331 * see whether the page bit testing has already
1332 * been done by the wake function.
1333 *
1334 * We can drop our reference to the page.
1335 */
1336 if (behavior == DROP)
1337 put_page(page);
1338
1339 /*
1340 * Note that until the "finish_wait()", or until
1341 * we see the WQ_FLAG_WOKEN flag, we need to
1342 * be very careful with the 'wait->flags', because
1343 * we may race with a waker that sets them.
1344 */
1345 for (;;) {
1346 unsigned int flags;
1347
1348 set_current_state(state);
1349
1350 /* Loop until we've been woken or interrupted */
1351 flags = smp_load_acquire(&wait->flags);
1352 if (!(flags & WQ_FLAG_WOKEN)) {
1353 if (signal_pending_state(state, current))
1354 break;
1355
1356 io_schedule();
1357 continue;
1358 }
1359
1360 /* If we were non-exclusive, we're done */
1361 if (behavior != EXCLUSIVE)
1362 break;
1363
1364 /* If the waker got the lock for us, we're done */
1365 if (flags & WQ_FLAG_DONE)
1366 break;
1367
1368 /*
1369 * Otherwise, if we're getting the lock, we need to
1370 * try to get it ourselves.
1371 *
1372 * And if that fails, we'll have to retry this all.
1373 */
1374 if (unlikely(test_and_set_bit(bit_nr, &page->flags)))
1375 goto repeat;
1376
1377 wait->flags |= WQ_FLAG_DONE;
1378 break;
1379 }
1380
1381 /*
1382 * If a signal happened, this 'finish_wait()' may remove the last
1383 * waiter from the wait-queues, but the PageWaiters bit will remain
1384 * set. That's ok. The next wakeup will take care of it, and trying
1385 * to do it here would be difficult and prone to races.
1386 */
1387 finish_wait(q, wait);
1388
1389 if (thrashing) {
1390 if (delayacct)
1391 delayacct_thrashing_end();
1392 psi_memstall_leave(&pflags);
1393 }
1394
1395 /*
1396 * NOTE! The wait->flags weren't stable until we've done the
1397 * 'finish_wait()', and we could have exited the loop above due
1398 * to a signal, and had a wakeup event happen after the signal
1399 * test but before the 'finish_wait()'.
1400 *
1401 * So only after the finish_wait() can we reliably determine
1402 * if we got woken up or not, so we can now figure out the final
1403 * return value based on that state without races.
1404 *
1405 * Also note that WQ_FLAG_WOKEN is sufficient for a non-exclusive
1406 * waiter, but an exclusive one requires WQ_FLAG_DONE.
1407 */
1408 if (behavior == EXCLUSIVE)
1409 return wait->flags & WQ_FLAG_DONE ? 0 : -EINTR;
1410
1411 return wait->flags & WQ_FLAG_WOKEN ? 0 : -EINTR;
1412 }
1413
wait_on_page_bit(struct page * page,int bit_nr)1414 void wait_on_page_bit(struct page *page, int bit_nr)
1415 {
1416 wait_queue_head_t *q = page_waitqueue(page);
1417 wait_on_page_bit_common(q, page, bit_nr, TASK_UNINTERRUPTIBLE, SHARED);
1418 }
1419 EXPORT_SYMBOL(wait_on_page_bit);
1420
wait_on_page_bit_killable(struct page * page,int bit_nr)1421 int wait_on_page_bit_killable(struct page *page, int bit_nr)
1422 {
1423 wait_queue_head_t *q = page_waitqueue(page);
1424 return wait_on_page_bit_common(q, page, bit_nr, TASK_KILLABLE, SHARED);
1425 }
1426 EXPORT_SYMBOL(wait_on_page_bit_killable);
1427
1428 /**
1429 * put_and_wait_on_page_locked - Drop a reference and wait for it to be unlocked
1430 * @page: The page to wait for.
1431 * @state: The sleep state (TASK_KILLABLE, TASK_UNINTERRUPTIBLE, etc).
1432 *
1433 * The caller should hold a reference on @page. They expect the page to
1434 * become unlocked relatively soon, but do not wish to hold up migration
1435 * (for example) by holding the reference while waiting for the page to
1436 * come unlocked. After this function returns, the caller should not
1437 * dereference @page.
1438 *
1439 * Return: 0 if the page was unlocked or -EINTR if interrupted by a signal.
1440 */
put_and_wait_on_page_locked(struct page * page,int state)1441 int put_and_wait_on_page_locked(struct page *page, int state)
1442 {
1443 wait_queue_head_t *q;
1444
1445 page = compound_head(page);
1446 q = page_waitqueue(page);
1447 return wait_on_page_bit_common(q, page, PG_locked, state, DROP);
1448 }
1449
1450 /**
1451 * add_page_wait_queue - Add an arbitrary waiter to a page's wait queue
1452 * @page: Page defining the wait queue of interest
1453 * @waiter: Waiter to add to the queue
1454 *
1455 * Add an arbitrary @waiter to the wait queue for the nominated @page.
1456 */
add_page_wait_queue(struct page * page,wait_queue_entry_t * waiter)1457 void add_page_wait_queue(struct page *page, wait_queue_entry_t *waiter)
1458 {
1459 wait_queue_head_t *q = page_waitqueue(page);
1460 unsigned long flags;
1461
1462 spin_lock_irqsave(&q->lock, flags);
1463 __add_wait_queue_entry_tail(q, waiter);
1464 SetPageWaiters(page);
1465 spin_unlock_irqrestore(&q->lock, flags);
1466 }
1467 EXPORT_SYMBOL_GPL(add_page_wait_queue);
1468
1469 #ifndef clear_bit_unlock_is_negative_byte
1470
1471 /*
1472 * PG_waiters is the high bit in the same byte as PG_lock.
1473 *
1474 * On x86 (and on many other architectures), we can clear PG_lock and
1475 * test the sign bit at the same time. But if the architecture does
1476 * not support that special operation, we just do this all by hand
1477 * instead.
1478 *
1479 * The read of PG_waiters has to be after (or concurrently with) PG_locked
1480 * being cleared, but a memory barrier should be unnecessary since it is
1481 * in the same byte as PG_locked.
1482 */
clear_bit_unlock_is_negative_byte(long nr,volatile void * mem)1483 static inline bool clear_bit_unlock_is_negative_byte(long nr, volatile void *mem)
1484 {
1485 clear_bit_unlock(nr, mem);
1486 /* smp_mb__after_atomic(); */
1487 return test_bit(PG_waiters, mem);
1488 }
1489
1490 #endif
1491
1492 /**
1493 * unlock_page - unlock a locked page
1494 * @page: the page
1495 *
1496 * Unlocks the page and wakes up sleepers in wait_on_page_locked().
1497 * Also wakes sleepers in wait_on_page_writeback() because the wakeup
1498 * mechanism between PageLocked pages and PageWriteback pages is shared.
1499 * But that's OK - sleepers in wait_on_page_writeback() just go back to sleep.
1500 *
1501 * Note that this depends on PG_waiters being the sign bit in the byte
1502 * that contains PG_locked - thus the BUILD_BUG_ON(). That allows us to
1503 * clear the PG_locked bit and test PG_waiters at the same time fairly
1504 * portably (architectures that do LL/SC can test any bit, while x86 can
1505 * test the sign bit).
1506 */
unlock_page(struct page * page)1507 void unlock_page(struct page *page)
1508 {
1509 BUILD_BUG_ON(PG_waiters != 7);
1510 page = compound_head(page);
1511 VM_BUG_ON_PAGE(!PageLocked(page), page);
1512 if (clear_bit_unlock_is_negative_byte(PG_locked, &page->flags))
1513 wake_up_page_bit(page, PG_locked);
1514 }
1515 EXPORT_SYMBOL(unlock_page);
1516
1517 /**
1518 * end_page_private_2 - Clear PG_private_2 and release any waiters
1519 * @page: The page
1520 *
1521 * Clear the PG_private_2 bit on a page and wake up any sleepers waiting for
1522 * this. The page ref held for PG_private_2 being set is released.
1523 *
1524 * This is, for example, used when a netfs page is being written to a local
1525 * disk cache, thereby allowing writes to the cache for the same page to be
1526 * serialised.
1527 */
end_page_private_2(struct page * page)1528 void end_page_private_2(struct page *page)
1529 {
1530 page = compound_head(page);
1531 VM_BUG_ON_PAGE(!PagePrivate2(page), page);
1532 clear_bit_unlock(PG_private_2, &page->flags);
1533 wake_up_page_bit(page, PG_private_2);
1534 put_page(page);
1535 }
1536 EXPORT_SYMBOL(end_page_private_2);
1537
1538 /**
1539 * wait_on_page_private_2 - Wait for PG_private_2 to be cleared on a page
1540 * @page: The page to wait on
1541 *
1542 * Wait for PG_private_2 (aka PG_fscache) to be cleared on a page.
1543 */
wait_on_page_private_2(struct page * page)1544 void wait_on_page_private_2(struct page *page)
1545 {
1546 page = compound_head(page);
1547 while (PagePrivate2(page))
1548 wait_on_page_bit(page, PG_private_2);
1549 }
1550 EXPORT_SYMBOL(wait_on_page_private_2);
1551
1552 /**
1553 * wait_on_page_private_2_killable - Wait for PG_private_2 to be cleared on a page
1554 * @page: The page to wait on
1555 *
1556 * Wait for PG_private_2 (aka PG_fscache) to be cleared on a page or until a
1557 * fatal signal is received by the calling task.
1558 *
1559 * Return:
1560 * - 0 if successful.
1561 * - -EINTR if a fatal signal was encountered.
1562 */
wait_on_page_private_2_killable(struct page * page)1563 int wait_on_page_private_2_killable(struct page *page)
1564 {
1565 int ret = 0;
1566
1567 page = compound_head(page);
1568 while (PagePrivate2(page)) {
1569 ret = wait_on_page_bit_killable(page, PG_private_2);
1570 if (ret < 0)
1571 break;
1572 }
1573
1574 return ret;
1575 }
1576 EXPORT_SYMBOL(wait_on_page_private_2_killable);
1577
1578 /**
1579 * end_page_writeback - end writeback against a page
1580 * @page: the page
1581 */
end_page_writeback(struct page * page)1582 void end_page_writeback(struct page *page)
1583 {
1584 /*
1585 * TestClearPageReclaim could be used here but it is an atomic
1586 * operation and overkill in this particular case. Failing to
1587 * shuffle a page marked for immediate reclaim is too mild to
1588 * justify taking an atomic operation penalty at the end of
1589 * ever page writeback.
1590 */
1591 if (PageReclaim(page)) {
1592 ClearPageReclaim(page);
1593 rotate_reclaimable_page(page);
1594 }
1595
1596 /*
1597 * Writeback does not hold a page reference of its own, relying
1598 * on truncation to wait for the clearing of PG_writeback.
1599 * But here we must make sure that the page is not freed and
1600 * reused before the wake_up_page().
1601 */
1602 get_page(page);
1603 if (!test_clear_page_writeback(page))
1604 BUG();
1605
1606 smp_mb__after_atomic();
1607 wake_up_page(page, PG_writeback);
1608 put_page(page);
1609 }
1610 EXPORT_SYMBOL(end_page_writeback);
1611
1612 /*
1613 * After completing I/O on a page, call this routine to update the page
1614 * flags appropriately
1615 */
page_endio(struct page * page,bool is_write,int err)1616 void page_endio(struct page *page, bool is_write, int err)
1617 {
1618 if (!is_write) {
1619 if (!err) {
1620 SetPageUptodate(page);
1621 } else {
1622 ClearPageUptodate(page);
1623 SetPageError(page);
1624 }
1625 unlock_page(page);
1626 } else {
1627 if (err) {
1628 struct address_space *mapping;
1629
1630 SetPageError(page);
1631 mapping = page_mapping(page);
1632 if (mapping)
1633 mapping_set_error(mapping, err);
1634 }
1635 end_page_writeback(page);
1636 }
1637 }
1638 EXPORT_SYMBOL_GPL(page_endio);
1639
1640 /**
1641 * __lock_page - get a lock on the page, assuming we need to sleep to get it
1642 * @__page: the page to lock
1643 */
__lock_page(struct page * __page)1644 void __lock_page(struct page *__page)
1645 {
1646 struct page *page = compound_head(__page);
1647 wait_queue_head_t *q = page_waitqueue(page);
1648 wait_on_page_bit_common(q, page, PG_locked, TASK_UNINTERRUPTIBLE,
1649 EXCLUSIVE);
1650 }
1651 EXPORT_SYMBOL(__lock_page);
1652
__lock_page_killable(struct page * __page)1653 int __lock_page_killable(struct page *__page)
1654 {
1655 struct page *page = compound_head(__page);
1656 wait_queue_head_t *q = page_waitqueue(page);
1657 return wait_on_page_bit_common(q, page, PG_locked, TASK_KILLABLE,
1658 EXCLUSIVE);
1659 }
1660 EXPORT_SYMBOL_GPL(__lock_page_killable);
1661
__lock_page_async(struct page * page,struct wait_page_queue * wait)1662 int __lock_page_async(struct page *page, struct wait_page_queue *wait)
1663 {
1664 struct wait_queue_head *q = page_waitqueue(page);
1665 int ret = 0;
1666
1667 wait->page = page;
1668 wait->bit_nr = PG_locked;
1669
1670 spin_lock_irq(&q->lock);
1671 __add_wait_queue_entry_tail(q, &wait->wait);
1672 SetPageWaiters(page);
1673 ret = !trylock_page(page);
1674 /*
1675 * If we were successful now, we know we're still on the
1676 * waitqueue as we're still under the lock. This means it's
1677 * safe to remove and return success, we know the callback
1678 * isn't going to trigger.
1679 */
1680 if (!ret)
1681 __remove_wait_queue(q, &wait->wait);
1682 else
1683 ret = -EIOCBQUEUED;
1684 spin_unlock_irq(&q->lock);
1685 return ret;
1686 }
1687
1688 /*
1689 * Return values:
1690 * 1 - page is locked; mmap_lock is still held.
1691 * 0 - page is not locked.
1692 * mmap_lock has been released (mmap_read_unlock(), unless flags had both
1693 * FAULT_FLAG_ALLOW_RETRY and FAULT_FLAG_RETRY_NOWAIT set, in
1694 * which case mmap_lock is still held.
1695 *
1696 * If neither ALLOW_RETRY nor KILLABLE are set, will always return 1
1697 * with the page locked and the mmap_lock unperturbed.
1698 */
__lock_page_or_retry(struct page * page,struct mm_struct * mm,unsigned int flags)1699 int __lock_page_or_retry(struct page *page, struct mm_struct *mm,
1700 unsigned int flags)
1701 {
1702 if (fault_flag_allow_retry_first(flags)) {
1703 /*
1704 * CAUTION! In this case, mmap_lock is not released
1705 * even though return 0.
1706 */
1707 if (flags & FAULT_FLAG_RETRY_NOWAIT)
1708 return 0;
1709
1710 mmap_read_unlock(mm);
1711 if (flags & FAULT_FLAG_KILLABLE)
1712 wait_on_page_locked_killable(page);
1713 else
1714 wait_on_page_locked(page);
1715 return 0;
1716 }
1717 if (flags & FAULT_FLAG_KILLABLE) {
1718 int ret;
1719
1720 ret = __lock_page_killable(page);
1721 if (ret) {
1722 mmap_read_unlock(mm);
1723 return 0;
1724 }
1725 } else {
1726 __lock_page(page);
1727 }
1728 return 1;
1729
1730 }
1731
1732 /**
1733 * page_cache_next_miss() - Find the next gap in the page cache.
1734 * @mapping: Mapping.
1735 * @index: Index.
1736 * @max_scan: Maximum range to search.
1737 *
1738 * Search the range [index, min(index + max_scan - 1, ULONG_MAX)] for the
1739 * gap with the lowest index.
1740 *
1741 * This function may be called under the rcu_read_lock. However, this will
1742 * not atomically search a snapshot of the cache at a single point in time.
1743 * For example, if a gap is created at index 5, then subsequently a gap is
1744 * created at index 10, page_cache_next_miss covering both indices may
1745 * return 10 if called under the rcu_read_lock.
1746 *
1747 * Return: The index of the gap if found, otherwise an index outside the
1748 * range specified (in which case 'return - index >= max_scan' will be true).
1749 * In the rare case of index wrap-around, 0 will be returned.
1750 */
page_cache_next_miss(struct address_space * mapping,pgoff_t index,unsigned long max_scan)1751 pgoff_t page_cache_next_miss(struct address_space *mapping,
1752 pgoff_t index, unsigned long max_scan)
1753 {
1754 XA_STATE(xas, &mapping->i_pages, index);
1755
1756 while (max_scan--) {
1757 void *entry = xas_next(&xas);
1758 if (!entry || xa_is_value(entry))
1759 break;
1760 if (xas.xa_index == 0)
1761 break;
1762 }
1763
1764 return xas.xa_index;
1765 }
1766 EXPORT_SYMBOL(page_cache_next_miss);
1767
1768 /**
1769 * page_cache_prev_miss() - Find the previous gap in the page cache.
1770 * @mapping: Mapping.
1771 * @index: Index.
1772 * @max_scan: Maximum range to search.
1773 *
1774 * Search the range [max(index - max_scan + 1, 0), index] for the
1775 * gap with the highest index.
1776 *
1777 * This function may be called under the rcu_read_lock. However, this will
1778 * not atomically search a snapshot of the cache at a single point in time.
1779 * For example, if a gap is created at index 10, then subsequently a gap is
1780 * created at index 5, page_cache_prev_miss() covering both indices may
1781 * return 5 if called under the rcu_read_lock.
1782 *
1783 * Return: The index of the gap if found, otherwise an index outside the
1784 * range specified (in which case 'index - return >= max_scan' will be true).
1785 * In the rare case of wrap-around, ULONG_MAX will be returned.
1786 */
page_cache_prev_miss(struct address_space * mapping,pgoff_t index,unsigned long max_scan)1787 pgoff_t page_cache_prev_miss(struct address_space *mapping,
1788 pgoff_t index, unsigned long max_scan)
1789 {
1790 XA_STATE(xas, &mapping->i_pages, index);
1791
1792 while (max_scan--) {
1793 void *entry = xas_prev(&xas);
1794 if (!entry || xa_is_value(entry))
1795 break;
1796 if (xas.xa_index == ULONG_MAX)
1797 break;
1798 }
1799
1800 return xas.xa_index;
1801 }
1802 EXPORT_SYMBOL(page_cache_prev_miss);
1803
1804 /*
1805 * mapping_get_entry - Get a page cache entry.
1806 * @mapping: the address_space to search
1807 * @index: The page cache index.
1808 *
1809 * Looks up the page cache slot at @mapping & @index. If there is a
1810 * page cache page, the head page is returned with an increased refcount.
1811 *
1812 * If the slot holds a shadow entry of a previously evicted page, or a
1813 * swap entry from shmem/tmpfs, it is returned.
1814 *
1815 * Return: The head page or shadow entry, %NULL if nothing is found.
1816 */
mapping_get_entry(struct address_space * mapping,pgoff_t index)1817 static struct page *mapping_get_entry(struct address_space *mapping,
1818 pgoff_t index)
1819 {
1820 XA_STATE(xas, &mapping->i_pages, index);
1821 struct page *page;
1822
1823 rcu_read_lock();
1824 repeat:
1825 xas_reset(&xas);
1826 page = xas_load(&xas);
1827 if (xas_retry(&xas, page))
1828 goto repeat;
1829 /*
1830 * A shadow entry of a recently evicted page, or a swap entry from
1831 * shmem/tmpfs. Return it without attempting to raise page count.
1832 */
1833 if (!page || xa_is_value(page))
1834 goto out;
1835
1836 if (!page_cache_get_speculative(page))
1837 goto repeat;
1838
1839 /*
1840 * Has the page moved or been split?
1841 * This is part of the lockless pagecache protocol. See
1842 * include/linux/pagemap.h for details.
1843 */
1844 if (unlikely(page != xas_reload(&xas))) {
1845 put_page(page);
1846 goto repeat;
1847 }
1848 out:
1849 rcu_read_unlock();
1850
1851 return page;
1852 }
1853
1854 /**
1855 * pagecache_get_page - Find and get a reference to a page.
1856 * @mapping: The address_space to search.
1857 * @index: The page index.
1858 * @fgp_flags: %FGP flags modify how the page is returned.
1859 * @gfp_mask: Memory allocation flags to use if %FGP_CREAT is specified.
1860 *
1861 * Looks up the page cache entry at @mapping & @index.
1862 *
1863 * @fgp_flags can be zero or more of these flags:
1864 *
1865 * * %FGP_ACCESSED - The page will be marked accessed.
1866 * * %FGP_LOCK - The page is returned locked.
1867 * * %FGP_HEAD - If the page is present and a THP, return the head page
1868 * rather than the exact page specified by the index.
1869 * * %FGP_ENTRY - If there is a shadow / swap / DAX entry, return it
1870 * instead of allocating a new page to replace it.
1871 * * %FGP_CREAT - If no page is present then a new page is allocated using
1872 * @gfp_mask and added to the page cache and the VM's LRU list.
1873 * The page is returned locked and with an increased refcount.
1874 * * %FGP_FOR_MMAP - The caller wants to do its own locking dance if the
1875 * page is already in cache. If the page was allocated, unlock it before
1876 * returning so the caller can do the same dance.
1877 * * %FGP_WRITE - The page will be written
1878 * * %FGP_NOFS - __GFP_FS will get cleared in gfp mask
1879 * * %FGP_NOWAIT - Don't get blocked by page lock
1880 *
1881 * If %FGP_LOCK or %FGP_CREAT are specified then the function may sleep even
1882 * if the %GFP flags specified for %FGP_CREAT are atomic.
1883 *
1884 * If there is a page cache page, it is returned with an increased refcount.
1885 *
1886 * Return: The found page or %NULL otherwise.
1887 */
pagecache_get_page(struct address_space * mapping,pgoff_t index,int fgp_flags,gfp_t gfp_mask)1888 struct page *pagecache_get_page(struct address_space *mapping, pgoff_t index,
1889 int fgp_flags, gfp_t gfp_mask)
1890 {
1891 struct page *page;
1892
1893 repeat:
1894 page = mapping_get_entry(mapping, index);
1895 if (xa_is_value(page)) {
1896 if (fgp_flags & FGP_ENTRY)
1897 return page;
1898 page = NULL;
1899 }
1900 if (!page)
1901 goto no_page;
1902
1903 if (fgp_flags & FGP_LOCK) {
1904 if (fgp_flags & FGP_NOWAIT) {
1905 if (!trylock_page(page)) {
1906 put_page(page);
1907 return NULL;
1908 }
1909 } else {
1910 lock_page(page);
1911 }
1912
1913 /* Has the page been truncated? */
1914 if (unlikely(page->mapping != mapping)) {
1915 unlock_page(page);
1916 put_page(page);
1917 goto repeat;
1918 }
1919 VM_BUG_ON_PAGE(!thp_contains(page, index), page);
1920 }
1921
1922 if (fgp_flags & FGP_ACCESSED)
1923 mark_page_accessed(page);
1924 else if (fgp_flags & FGP_WRITE) {
1925 /* Clear idle flag for buffer write */
1926 if (page_is_idle(page))
1927 clear_page_idle(page);
1928 }
1929 if (!(fgp_flags & FGP_HEAD))
1930 page = find_subpage(page, index);
1931
1932 no_page:
1933 if (!page && (fgp_flags & FGP_CREAT)) {
1934 int err;
1935 if ((fgp_flags & FGP_WRITE) && mapping_can_writeback(mapping))
1936 gfp_mask |= __GFP_WRITE;
1937 if (fgp_flags & FGP_NOFS)
1938 gfp_mask &= ~__GFP_FS;
1939
1940 page = __page_cache_alloc(gfp_mask);
1941 if (!page)
1942 return NULL;
1943
1944 if (WARN_ON_ONCE(!(fgp_flags & (FGP_LOCK | FGP_FOR_MMAP))))
1945 fgp_flags |= FGP_LOCK;
1946
1947 /* Init accessed so avoid atomic mark_page_accessed later */
1948 if (fgp_flags & FGP_ACCESSED)
1949 __SetPageReferenced(page);
1950
1951 err = add_to_page_cache_lru(page, mapping, index, gfp_mask);
1952 if (unlikely(err)) {
1953 put_page(page);
1954 page = NULL;
1955 if (err == -EEXIST)
1956 goto repeat;
1957 }
1958
1959 /*
1960 * add_to_page_cache_lru locks the page, and for mmap we expect
1961 * an unlocked page.
1962 */
1963 if (page && (fgp_flags & FGP_FOR_MMAP))
1964 unlock_page(page);
1965 }
1966
1967 return page;
1968 }
1969 EXPORT_SYMBOL(pagecache_get_page);
1970
find_get_entry(struct xa_state * xas,pgoff_t max,xa_mark_t mark)1971 static inline struct page *find_get_entry(struct xa_state *xas, pgoff_t max,
1972 xa_mark_t mark)
1973 {
1974 struct page *page;
1975
1976 retry:
1977 if (mark == XA_PRESENT)
1978 page = xas_find(xas, max);
1979 else
1980 page = xas_find_marked(xas, max, mark);
1981
1982 if (xas_retry(xas, page))
1983 goto retry;
1984 /*
1985 * A shadow entry of a recently evicted page, a swap
1986 * entry from shmem/tmpfs or a DAX entry. Return it
1987 * without attempting to raise page count.
1988 */
1989 if (!page || xa_is_value(page))
1990 return page;
1991
1992 if (!page_cache_get_speculative(page))
1993 goto reset;
1994
1995 /* Has the page moved or been split? */
1996 if (unlikely(page != xas_reload(xas))) {
1997 put_page(page);
1998 goto reset;
1999 }
2000
2001 return page;
2002 reset:
2003 xas_reset(xas);
2004 goto retry;
2005 }
2006
2007 /**
2008 * find_get_entries - gang pagecache lookup
2009 * @mapping: The address_space to search
2010 * @start: The starting page cache index
2011 * @end: The final page index (inclusive).
2012 * @pvec: Where the resulting entries are placed.
2013 * @indices: The cache indices corresponding to the entries in @entries
2014 *
2015 * find_get_entries() will search for and return a batch of entries in
2016 * the mapping. The entries are placed in @pvec. find_get_entries()
2017 * takes a reference on any actual pages it returns.
2018 *
2019 * The search returns a group of mapping-contiguous page cache entries
2020 * with ascending indexes. There may be holes in the indices due to
2021 * not-present pages.
2022 *
2023 * Any shadow entries of evicted pages, or swap entries from
2024 * shmem/tmpfs, are included in the returned array.
2025 *
2026 * If it finds a Transparent Huge Page, head or tail, find_get_entries()
2027 * stops at that page: the caller is likely to have a better way to handle
2028 * the compound page as a whole, and then skip its extent, than repeatedly
2029 * calling find_get_entries() to return all its tails.
2030 *
2031 * Return: the number of pages and shadow entries which were found.
2032 */
find_get_entries(struct address_space * mapping,pgoff_t start,pgoff_t end,struct pagevec * pvec,pgoff_t * indices)2033 unsigned find_get_entries(struct address_space *mapping, pgoff_t start,
2034 pgoff_t end, struct pagevec *pvec, pgoff_t *indices)
2035 {
2036 XA_STATE(xas, &mapping->i_pages, start);
2037 struct page *page;
2038 unsigned int ret = 0;
2039 unsigned nr_entries = PAGEVEC_SIZE;
2040
2041 rcu_read_lock();
2042 while ((page = find_get_entry(&xas, end, XA_PRESENT))) {
2043 /*
2044 * Terminate early on finding a THP, to allow the caller to
2045 * handle it all at once; but continue if this is hugetlbfs.
2046 */
2047 if (!xa_is_value(page) && PageTransHuge(page) &&
2048 !PageHuge(page)) {
2049 page = find_subpage(page, xas.xa_index);
2050 nr_entries = ret + 1;
2051 }
2052
2053 indices[ret] = xas.xa_index;
2054 pvec->pages[ret] = page;
2055 if (++ret == nr_entries)
2056 break;
2057 }
2058 rcu_read_unlock();
2059
2060 pvec->nr = ret;
2061 return ret;
2062 }
2063
2064 /**
2065 * find_lock_entries - Find a batch of pagecache entries.
2066 * @mapping: The address_space to search.
2067 * @start: The starting page cache index.
2068 * @end: The final page index (inclusive).
2069 * @pvec: Where the resulting entries are placed.
2070 * @indices: The cache indices of the entries in @pvec.
2071 *
2072 * find_lock_entries() will return a batch of entries from @mapping.
2073 * Swap, shadow and DAX entries are included. Pages are returned
2074 * locked and with an incremented refcount. Pages which are locked by
2075 * somebody else or under writeback are skipped. Only the head page of
2076 * a THP is returned. Pages which are partially outside the range are
2077 * not returned.
2078 *
2079 * The entries have ascending indexes. The indices may not be consecutive
2080 * due to not-present entries, THP pages, pages which could not be locked
2081 * or pages under writeback.
2082 *
2083 * Return: The number of entries which were found.
2084 */
find_lock_entries(struct address_space * mapping,pgoff_t start,pgoff_t end,struct pagevec * pvec,pgoff_t * indices)2085 unsigned find_lock_entries(struct address_space *mapping, pgoff_t start,
2086 pgoff_t end, struct pagevec *pvec, pgoff_t *indices)
2087 {
2088 XA_STATE(xas, &mapping->i_pages, start);
2089 struct page *page;
2090
2091 rcu_read_lock();
2092 while ((page = find_get_entry(&xas, end, XA_PRESENT))) {
2093 if (!xa_is_value(page)) {
2094 if (page->index < start)
2095 goto put;
2096 VM_BUG_ON_PAGE(page->index != xas.xa_index, page);
2097 if (page->index + thp_nr_pages(page) - 1 > end)
2098 goto put;
2099 if (!trylock_page(page))
2100 goto put;
2101 if (page->mapping != mapping || PageWriteback(page))
2102 goto unlock;
2103 VM_BUG_ON_PAGE(!thp_contains(page, xas.xa_index),
2104 page);
2105 }
2106 indices[pvec->nr] = xas.xa_index;
2107 if (!pagevec_add(pvec, page))
2108 break;
2109 goto next;
2110 unlock:
2111 unlock_page(page);
2112 put:
2113 put_page(page);
2114 next:
2115 if (!xa_is_value(page) && PageTransHuge(page)) {
2116 unsigned int nr_pages = thp_nr_pages(page);
2117
2118 /* Final THP may cross MAX_LFS_FILESIZE on 32-bit */
2119 xas_set(&xas, page->index + nr_pages);
2120 if (xas.xa_index < nr_pages)
2121 break;
2122 }
2123 }
2124 rcu_read_unlock();
2125
2126 return pagevec_count(pvec);
2127 }
2128
2129 /**
2130 * find_get_pages_range - gang pagecache lookup
2131 * @mapping: The address_space to search
2132 * @start: The starting page index
2133 * @end: The final page index (inclusive)
2134 * @nr_pages: The maximum number of pages
2135 * @pages: Where the resulting pages are placed
2136 *
2137 * find_get_pages_range() will search for and return a group of up to @nr_pages
2138 * pages in the mapping starting at index @start and up to index @end
2139 * (inclusive). The pages are placed at @pages. find_get_pages_range() takes
2140 * a reference against the returned pages.
2141 *
2142 * The search returns a group of mapping-contiguous pages with ascending
2143 * indexes. There may be holes in the indices due to not-present pages.
2144 * We also update @start to index the next page for the traversal.
2145 *
2146 * Return: the number of pages which were found. If this number is
2147 * smaller than @nr_pages, the end of specified range has been
2148 * reached.
2149 */
find_get_pages_range(struct address_space * mapping,pgoff_t * start,pgoff_t end,unsigned int nr_pages,struct page ** pages)2150 unsigned find_get_pages_range(struct address_space *mapping, pgoff_t *start,
2151 pgoff_t end, unsigned int nr_pages,
2152 struct page **pages)
2153 {
2154 XA_STATE(xas, &mapping->i_pages, *start);
2155 struct page *page;
2156 unsigned ret = 0;
2157
2158 if (unlikely(!nr_pages))
2159 return 0;
2160
2161 rcu_read_lock();
2162 while ((page = find_get_entry(&xas, end, XA_PRESENT))) {
2163 /* Skip over shadow, swap and DAX entries */
2164 if (xa_is_value(page))
2165 continue;
2166
2167 pages[ret] = find_subpage(page, xas.xa_index);
2168 if (++ret == nr_pages) {
2169 *start = xas.xa_index + 1;
2170 goto out;
2171 }
2172 }
2173
2174 /*
2175 * We come here when there is no page beyond @end. We take care to not
2176 * overflow the index @start as it confuses some of the callers. This
2177 * breaks the iteration when there is a page at index -1 but that is
2178 * already broken anyway.
2179 */
2180 if (end == (pgoff_t)-1)
2181 *start = (pgoff_t)-1;
2182 else
2183 *start = end + 1;
2184 out:
2185 rcu_read_unlock();
2186
2187 return ret;
2188 }
2189
2190 /**
2191 * find_get_pages_contig - gang contiguous pagecache lookup
2192 * @mapping: The address_space to search
2193 * @index: The starting page index
2194 * @nr_pages: The maximum number of pages
2195 * @pages: Where the resulting pages are placed
2196 *
2197 * find_get_pages_contig() works exactly like find_get_pages(), except
2198 * that the returned number of pages are guaranteed to be contiguous.
2199 *
2200 * Return: the number of pages which were found.
2201 */
find_get_pages_contig(struct address_space * mapping,pgoff_t index,unsigned int nr_pages,struct page ** pages)2202 unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t index,
2203 unsigned int nr_pages, struct page **pages)
2204 {
2205 XA_STATE(xas, &mapping->i_pages, index);
2206 struct page *page;
2207 unsigned int ret = 0;
2208
2209 if (unlikely(!nr_pages))
2210 return 0;
2211
2212 rcu_read_lock();
2213 for (page = xas_load(&xas); page; page = xas_next(&xas)) {
2214 if (xas_retry(&xas, page))
2215 continue;
2216 /*
2217 * If the entry has been swapped out, we can stop looking.
2218 * No current caller is looking for DAX entries.
2219 */
2220 if (xa_is_value(page))
2221 break;
2222
2223 if (!page_cache_get_speculative(page))
2224 goto retry;
2225
2226 /* Has the page moved or been split? */
2227 if (unlikely(page != xas_reload(&xas)))
2228 goto put_page;
2229
2230 pages[ret] = find_subpage(page, xas.xa_index);
2231 if (++ret == nr_pages)
2232 break;
2233 continue;
2234 put_page:
2235 put_page(page);
2236 retry:
2237 xas_reset(&xas);
2238 }
2239 rcu_read_unlock();
2240 return ret;
2241 }
2242 EXPORT_SYMBOL(find_get_pages_contig);
2243
2244 /**
2245 * find_get_pages_range_tag - Find and return head pages matching @tag.
2246 * @mapping: the address_space to search
2247 * @index: the starting page index
2248 * @end: The final page index (inclusive)
2249 * @tag: the tag index
2250 * @nr_pages: the maximum number of pages
2251 * @pages: where the resulting pages are placed
2252 *
2253 * Like find_get_pages(), except we only return head pages which are tagged
2254 * with @tag. @index is updated to the index immediately after the last
2255 * page we return, ready for the next iteration.
2256 *
2257 * Return: the number of pages which were found.
2258 */
find_get_pages_range_tag(struct address_space * mapping,pgoff_t * index,pgoff_t end,xa_mark_t tag,unsigned int nr_pages,struct page ** pages)2259 unsigned find_get_pages_range_tag(struct address_space *mapping, pgoff_t *index,
2260 pgoff_t end, xa_mark_t tag, unsigned int nr_pages,
2261 struct page **pages)
2262 {
2263 XA_STATE(xas, &mapping->i_pages, *index);
2264 struct page *page;
2265 unsigned ret = 0;
2266
2267 if (unlikely(!nr_pages))
2268 return 0;
2269
2270 rcu_read_lock();
2271 while ((page = find_get_entry(&xas, end, tag))) {
2272 /*
2273 * Shadow entries should never be tagged, but this iteration
2274 * is lockless so there is a window for page reclaim to evict
2275 * a page we saw tagged. Skip over it.
2276 */
2277 if (xa_is_value(page))
2278 continue;
2279
2280 pages[ret] = page;
2281 if (++ret == nr_pages) {
2282 *index = page->index + thp_nr_pages(page);
2283 goto out;
2284 }
2285 }
2286
2287 /*
2288 * We come here when we got to @end. We take care to not overflow the
2289 * index @index as it confuses some of the callers. This breaks the
2290 * iteration when there is a page at index -1 but that is already
2291 * broken anyway.
2292 */
2293 if (end == (pgoff_t)-1)
2294 *index = (pgoff_t)-1;
2295 else
2296 *index = end + 1;
2297 out:
2298 rcu_read_unlock();
2299
2300 return ret;
2301 }
2302 EXPORT_SYMBOL(find_get_pages_range_tag);
2303
2304 /*
2305 * CD/DVDs are error prone. When a medium error occurs, the driver may fail
2306 * a _large_ part of the i/o request. Imagine the worst scenario:
2307 *
2308 * ---R__________________________________________B__________
2309 * ^ reading here ^ bad block(assume 4k)
2310 *
2311 * read(R) => miss => readahead(R...B) => media error => frustrating retries
2312 * => failing the whole request => read(R) => read(R+1) =>
2313 * readahead(R+1...B+1) => bang => read(R+2) => read(R+3) =>
2314 * readahead(R+3...B+2) => bang => read(R+3) => read(R+4) =>
2315 * readahead(R+4...B+3) => bang => read(R+4) => read(R+5) => ......
2316 *
2317 * It is going insane. Fix it by quickly scaling down the readahead size.
2318 */
shrink_readahead_size_eio(struct file_ra_state * ra)2319 static void shrink_readahead_size_eio(struct file_ra_state *ra)
2320 {
2321 ra->ra_pages /= 4;
2322 }
2323
2324 /*
2325 * filemap_get_read_batch - Get a batch of pages for read
2326 *
2327 * Get a batch of pages which represent a contiguous range of bytes
2328 * in the file. No tail pages will be returned. If @index is in the
2329 * middle of a THP, the entire THP will be returned. The last page in
2330 * the batch may have Readahead set or be not Uptodate so that the
2331 * caller can take the appropriate action.
2332 */
filemap_get_read_batch(struct address_space * mapping,pgoff_t index,pgoff_t max,struct pagevec * pvec)2333 static void filemap_get_read_batch(struct address_space *mapping,
2334 pgoff_t index, pgoff_t max, struct pagevec *pvec)
2335 {
2336 XA_STATE(xas, &mapping->i_pages, index);
2337 struct page *head;
2338
2339 rcu_read_lock();
2340 for (head = xas_load(&xas); head; head = xas_next(&xas)) {
2341 if (xas_retry(&xas, head))
2342 continue;
2343 if (xas.xa_index > max || xa_is_value(head))
2344 break;
2345 if (!page_cache_get_speculative(head))
2346 goto retry;
2347
2348 /* Has the page moved or been split? */
2349 if (unlikely(head != xas_reload(&xas)))
2350 goto put_page;
2351
2352 if (!pagevec_add(pvec, head))
2353 break;
2354 if (!PageUptodate(head))
2355 break;
2356 if (PageReadahead(head))
2357 break;
2358 xas.xa_index = head->index + thp_nr_pages(head) - 1;
2359 xas.xa_offset = (xas.xa_index >> xas.xa_shift) & XA_CHUNK_MASK;
2360 continue;
2361 put_page:
2362 put_page(head);
2363 retry:
2364 xas_reset(&xas);
2365 }
2366 rcu_read_unlock();
2367 }
2368
filemap_read_page(struct file * file,struct address_space * mapping,struct page * page)2369 static int filemap_read_page(struct file *file, struct address_space *mapping,
2370 struct page *page)
2371 {
2372 int error;
2373
2374 /*
2375 * A previous I/O error may have been due to temporary failures,
2376 * eg. multipath errors. PG_error will be set again if readpage
2377 * fails.
2378 */
2379 ClearPageError(page);
2380 /* Start the actual read. The read will unlock the page. */
2381 error = mapping->a_ops->readpage(file, page);
2382 if (error)
2383 return error;
2384
2385 error = wait_on_page_locked_killable(page);
2386 if (error)
2387 return error;
2388 if (PageUptodate(page))
2389 return 0;
2390 shrink_readahead_size_eio(&file->f_ra);
2391 return -EIO;
2392 }
2393
filemap_range_uptodate(struct address_space * mapping,loff_t pos,struct iov_iter * iter,struct page * page)2394 static bool filemap_range_uptodate(struct address_space *mapping,
2395 loff_t pos, struct iov_iter *iter, struct page *page)
2396 {
2397 int count;
2398
2399 if (PageUptodate(page))
2400 return true;
2401 /* pipes can't handle partially uptodate pages */
2402 if (iov_iter_is_pipe(iter))
2403 return false;
2404 if (!mapping->a_ops->is_partially_uptodate)
2405 return false;
2406 if (mapping->host->i_blkbits >= (PAGE_SHIFT + thp_order(page)))
2407 return false;
2408
2409 count = iter->count;
2410 if (page_offset(page) > pos) {
2411 count -= page_offset(page) - pos;
2412 pos = 0;
2413 } else {
2414 pos -= page_offset(page);
2415 }
2416
2417 return mapping->a_ops->is_partially_uptodate(page, pos, count);
2418 }
2419
filemap_update_page(struct kiocb * iocb,struct address_space * mapping,struct iov_iter * iter,struct page * page)2420 static int filemap_update_page(struct kiocb *iocb,
2421 struct address_space *mapping, struct iov_iter *iter,
2422 struct page *page)
2423 {
2424 int error;
2425
2426 if (iocb->ki_flags & IOCB_NOWAIT) {
2427 if (!filemap_invalidate_trylock_shared(mapping))
2428 return -EAGAIN;
2429 } else {
2430 filemap_invalidate_lock_shared(mapping);
2431 }
2432
2433 if (!trylock_page(page)) {
2434 error = -EAGAIN;
2435 if (iocb->ki_flags & (IOCB_NOWAIT | IOCB_NOIO))
2436 goto unlock_mapping;
2437 if (!(iocb->ki_flags & IOCB_WAITQ)) {
2438 filemap_invalidate_unlock_shared(mapping);
2439 put_and_wait_on_page_locked(page, TASK_KILLABLE);
2440 return AOP_TRUNCATED_PAGE;
2441 }
2442 error = __lock_page_async(page, iocb->ki_waitq);
2443 if (error)
2444 goto unlock_mapping;
2445 }
2446
2447 error = AOP_TRUNCATED_PAGE;
2448 if (!page->mapping)
2449 goto unlock;
2450
2451 error = 0;
2452 if (filemap_range_uptodate(mapping, iocb->ki_pos, iter, page))
2453 goto unlock;
2454
2455 error = -EAGAIN;
2456 if (iocb->ki_flags & (IOCB_NOIO | IOCB_NOWAIT | IOCB_WAITQ))
2457 goto unlock;
2458
2459 error = filemap_read_page(iocb->ki_filp, mapping, page);
2460 goto unlock_mapping;
2461 unlock:
2462 unlock_page(page);
2463 unlock_mapping:
2464 filemap_invalidate_unlock_shared(mapping);
2465 if (error == AOP_TRUNCATED_PAGE)
2466 put_page(page);
2467 return error;
2468 }
2469
filemap_create_page(struct file * file,struct address_space * mapping,pgoff_t index,struct pagevec * pvec)2470 static int filemap_create_page(struct file *file,
2471 struct address_space *mapping, pgoff_t index,
2472 struct pagevec *pvec)
2473 {
2474 struct page *page;
2475 int error;
2476
2477 page = page_cache_alloc(mapping);
2478 if (!page)
2479 return -ENOMEM;
2480
2481 /*
2482 * Protect against truncate / hole punch. Grabbing invalidate_lock here
2483 * assures we cannot instantiate and bring uptodate new pagecache pages
2484 * after evicting page cache during truncate and before actually
2485 * freeing blocks. Note that we could release invalidate_lock after
2486 * inserting the page into page cache as the locked page would then be
2487 * enough to synchronize with hole punching. But there are code paths
2488 * such as filemap_update_page() filling in partially uptodate pages or
2489 * ->readpages() that need to hold invalidate_lock while mapping blocks
2490 * for IO so let's hold the lock here as well to keep locking rules
2491 * simple.
2492 */
2493 filemap_invalidate_lock_shared(mapping);
2494 error = add_to_page_cache_lru(page, mapping, index,
2495 mapping_gfp_constraint(mapping, GFP_KERNEL));
2496 if (error == -EEXIST)
2497 error = AOP_TRUNCATED_PAGE;
2498 if (error)
2499 goto error;
2500
2501 error = filemap_read_page(file, mapping, page);
2502 if (error)
2503 goto error;
2504
2505 filemap_invalidate_unlock_shared(mapping);
2506 pagevec_add(pvec, page);
2507 return 0;
2508 error:
2509 filemap_invalidate_unlock_shared(mapping);
2510 put_page(page);
2511 return error;
2512 }
2513
filemap_readahead(struct kiocb * iocb,struct file * file,struct address_space * mapping,struct page * page,pgoff_t last_index)2514 static int filemap_readahead(struct kiocb *iocb, struct file *file,
2515 struct address_space *mapping, struct page *page,
2516 pgoff_t last_index)
2517 {
2518 if (iocb->ki_flags & IOCB_NOIO)
2519 return -EAGAIN;
2520 page_cache_async_readahead(mapping, &file->f_ra, file, page,
2521 page->index, last_index - page->index);
2522 return 0;
2523 }
2524
filemap_get_pages(struct kiocb * iocb,struct iov_iter * iter,struct pagevec * pvec)2525 static int filemap_get_pages(struct kiocb *iocb, struct iov_iter *iter,
2526 struct pagevec *pvec)
2527 {
2528 struct file *filp = iocb->ki_filp;
2529 struct address_space *mapping = filp->f_mapping;
2530 struct file_ra_state *ra = &filp->f_ra;
2531 pgoff_t index = iocb->ki_pos >> PAGE_SHIFT;
2532 pgoff_t last_index;
2533 struct page *page;
2534 int err = 0;
2535
2536 last_index = DIV_ROUND_UP(iocb->ki_pos + iter->count, PAGE_SIZE);
2537 retry:
2538 if (fatal_signal_pending(current))
2539 return -EINTR;
2540
2541 filemap_get_read_batch(mapping, index, last_index, pvec);
2542 if (!pagevec_count(pvec)) {
2543 if (iocb->ki_flags & IOCB_NOIO)
2544 return -EAGAIN;
2545 page_cache_sync_readahead(mapping, ra, filp, index,
2546 last_index - index);
2547 filemap_get_read_batch(mapping, index, last_index, pvec);
2548 }
2549 if (!pagevec_count(pvec)) {
2550 if (iocb->ki_flags & (IOCB_NOWAIT | IOCB_WAITQ))
2551 return -EAGAIN;
2552 err = filemap_create_page(filp, mapping,
2553 iocb->ki_pos >> PAGE_SHIFT, pvec);
2554 if (err == AOP_TRUNCATED_PAGE)
2555 goto retry;
2556 return err;
2557 }
2558
2559 page = pvec->pages[pagevec_count(pvec) - 1];
2560 if (PageReadahead(page)) {
2561 err = filemap_readahead(iocb, filp, mapping, page, last_index);
2562 if (err)
2563 goto err;
2564 }
2565 if (!PageUptodate(page)) {
2566 if ((iocb->ki_flags & IOCB_WAITQ) && pagevec_count(pvec) > 1)
2567 iocb->ki_flags |= IOCB_NOWAIT;
2568 err = filemap_update_page(iocb, mapping, iter, page);
2569 if (err)
2570 goto err;
2571 }
2572
2573 return 0;
2574 err:
2575 if (err < 0)
2576 put_page(page);
2577 if (likely(--pvec->nr))
2578 return 0;
2579 if (err == AOP_TRUNCATED_PAGE)
2580 goto retry;
2581 return err;
2582 }
2583
2584 /**
2585 * filemap_read - Read data from the page cache.
2586 * @iocb: The iocb to read.
2587 * @iter: Destination for the data.
2588 * @already_read: Number of bytes already read by the caller.
2589 *
2590 * Copies data from the page cache. If the data is not currently present,
2591 * uses the readahead and readpage address_space operations to fetch it.
2592 *
2593 * Return: Total number of bytes copied, including those already read by
2594 * the caller. If an error happens before any bytes are copied, returns
2595 * a negative error number.
2596 */
filemap_read(struct kiocb * iocb,struct iov_iter * iter,ssize_t already_read)2597 ssize_t filemap_read(struct kiocb *iocb, struct iov_iter *iter,
2598 ssize_t already_read)
2599 {
2600 struct file *filp = iocb->ki_filp;
2601 struct file_ra_state *ra = &filp->f_ra;
2602 struct address_space *mapping = filp->f_mapping;
2603 struct inode *inode = mapping->host;
2604 struct pagevec pvec;
2605 int i, error = 0;
2606 bool writably_mapped;
2607 loff_t isize, end_offset;
2608
2609 if (unlikely(iocb->ki_pos >= inode->i_sb->s_maxbytes))
2610 return 0;
2611 if (unlikely(!iov_iter_count(iter)))
2612 return 0;
2613
2614 iov_iter_truncate(iter, inode->i_sb->s_maxbytes);
2615 pagevec_init(&pvec);
2616
2617 do {
2618 cond_resched();
2619
2620 /*
2621 * If we've already successfully copied some data, then we
2622 * can no longer safely return -EIOCBQUEUED. Hence mark
2623 * an async read NOWAIT at that point.
2624 */
2625 if ((iocb->ki_flags & IOCB_WAITQ) && already_read)
2626 iocb->ki_flags |= IOCB_NOWAIT;
2627
2628 error = filemap_get_pages(iocb, iter, &pvec);
2629 if (error < 0)
2630 break;
2631
2632 /*
2633 * i_size must be checked after we know the pages are Uptodate.
2634 *
2635 * Checking i_size after the check allows us to calculate
2636 * the correct value for "nr", which means the zero-filled
2637 * part of the page is not copied back to userspace (unless
2638 * another truncate extends the file - this is desired though).
2639 */
2640 isize = i_size_read(inode);
2641 if (unlikely(iocb->ki_pos >= isize))
2642 goto put_pages;
2643 end_offset = min_t(loff_t, isize, iocb->ki_pos + iter->count);
2644
2645 /*
2646 * Once we start copying data, we don't want to be touching any
2647 * cachelines that might be contended:
2648 */
2649 writably_mapped = mapping_writably_mapped(mapping);
2650
2651 /*
2652 * When a sequential read accesses a page several times, only
2653 * mark it as accessed the first time.
2654 */
2655 if (iocb->ki_pos >> PAGE_SHIFT !=
2656 ra->prev_pos >> PAGE_SHIFT)
2657 mark_page_accessed(pvec.pages[0]);
2658
2659 for (i = 0; i < pagevec_count(&pvec); i++) {
2660 struct page *page = pvec.pages[i];
2661 size_t page_size = thp_size(page);
2662 size_t offset = iocb->ki_pos & (page_size - 1);
2663 size_t bytes = min_t(loff_t, end_offset - iocb->ki_pos,
2664 page_size - offset);
2665 size_t copied;
2666
2667 if (end_offset < page_offset(page))
2668 break;
2669 if (i > 0)
2670 mark_page_accessed(page);
2671 /*
2672 * If users can be writing to this page using arbitrary
2673 * virtual addresses, take care about potential aliasing
2674 * before reading the page on the kernel side.
2675 */
2676 if (writably_mapped) {
2677 int j;
2678
2679 for (j = 0; j < thp_nr_pages(page); j++)
2680 flush_dcache_page(page + j);
2681 }
2682
2683 copied = copy_page_to_iter(page, offset, bytes, iter);
2684
2685 already_read += copied;
2686 iocb->ki_pos += copied;
2687 ra->prev_pos = iocb->ki_pos;
2688
2689 if (copied < bytes) {
2690 error = -EFAULT;
2691 break;
2692 }
2693 }
2694 put_pages:
2695 for (i = 0; i < pagevec_count(&pvec); i++)
2696 put_page(pvec.pages[i]);
2697 pagevec_reinit(&pvec);
2698 } while (iov_iter_count(iter) && iocb->ki_pos < isize && !error);
2699
2700 file_accessed(filp);
2701
2702 return already_read ? already_read : error;
2703 }
2704 EXPORT_SYMBOL_GPL(filemap_read);
2705
2706 /**
2707 * generic_file_read_iter - generic filesystem read routine
2708 * @iocb: kernel I/O control block
2709 * @iter: destination for the data read
2710 *
2711 * This is the "read_iter()" routine for all filesystems
2712 * that can use the page cache directly.
2713 *
2714 * The IOCB_NOWAIT flag in iocb->ki_flags indicates that -EAGAIN shall
2715 * be returned when no data can be read without waiting for I/O requests
2716 * to complete; it doesn't prevent readahead.
2717 *
2718 * The IOCB_NOIO flag in iocb->ki_flags indicates that no new I/O
2719 * requests shall be made for the read or for readahead. When no data
2720 * can be read, -EAGAIN shall be returned. When readahead would be
2721 * triggered, a partial, possibly empty read shall be returned.
2722 *
2723 * Return:
2724 * * number of bytes copied, even for partial reads
2725 * * negative error code (or 0 if IOCB_NOIO) if nothing was read
2726 */
2727 ssize_t
generic_file_read_iter(struct kiocb * iocb,struct iov_iter * iter)2728 generic_file_read_iter(struct kiocb *iocb, struct iov_iter *iter)
2729 {
2730 size_t count = iov_iter_count(iter);
2731 ssize_t retval = 0;
2732
2733 if (!count)
2734 return 0; /* skip atime */
2735
2736 if (iocb->ki_flags & IOCB_DIRECT) {
2737 struct file *file = iocb->ki_filp;
2738 struct address_space *mapping = file->f_mapping;
2739 struct inode *inode = mapping->host;
2740 loff_t size;
2741
2742 size = i_size_read(inode);
2743 if (iocb->ki_flags & IOCB_NOWAIT) {
2744 if (filemap_range_needs_writeback(mapping, iocb->ki_pos,
2745 iocb->ki_pos + count - 1))
2746 return -EAGAIN;
2747 } else {
2748 retval = filemap_write_and_wait_range(mapping,
2749 iocb->ki_pos,
2750 iocb->ki_pos + count - 1);
2751 if (retval < 0)
2752 return retval;
2753 }
2754
2755 file_accessed(file);
2756
2757 retval = mapping->a_ops->direct_IO(iocb, iter);
2758 if (retval >= 0) {
2759 iocb->ki_pos += retval;
2760 count -= retval;
2761 }
2762 if (retval != -EIOCBQUEUED)
2763 iov_iter_revert(iter, count - iov_iter_count(iter));
2764
2765 /*
2766 * Btrfs can have a short DIO read if we encounter
2767 * compressed extents, so if there was an error, or if
2768 * we've already read everything we wanted to, or if
2769 * there was a short read because we hit EOF, go ahead
2770 * and return. Otherwise fallthrough to buffered io for
2771 * the rest of the read. Buffered reads will not work for
2772 * DAX files, so don't bother trying.
2773 */
2774 if (retval < 0 || !count || iocb->ki_pos >= size ||
2775 IS_DAX(inode))
2776 return retval;
2777 }
2778
2779 return filemap_read(iocb, iter, retval);
2780 }
2781 EXPORT_SYMBOL(generic_file_read_iter);
2782
page_seek_hole_data(struct xa_state * xas,struct address_space * mapping,struct page * page,loff_t start,loff_t end,bool seek_data)2783 static inline loff_t page_seek_hole_data(struct xa_state *xas,
2784 struct address_space *mapping, struct page *page,
2785 loff_t start, loff_t end, bool seek_data)
2786 {
2787 const struct address_space_operations *ops = mapping->a_ops;
2788 size_t offset, bsz = i_blocksize(mapping->host);
2789
2790 if (xa_is_value(page) || PageUptodate(page))
2791 return seek_data ? start : end;
2792 if (!ops->is_partially_uptodate)
2793 return seek_data ? end : start;
2794
2795 xas_pause(xas);
2796 rcu_read_unlock();
2797 lock_page(page);
2798 if (unlikely(page->mapping != mapping))
2799 goto unlock;
2800
2801 offset = offset_in_thp(page, start) & ~(bsz - 1);
2802
2803 do {
2804 if (ops->is_partially_uptodate(page, offset, bsz) == seek_data)
2805 break;
2806 start = (start + bsz) & ~(bsz - 1);
2807 offset += bsz;
2808 } while (offset < thp_size(page));
2809 unlock:
2810 unlock_page(page);
2811 rcu_read_lock();
2812 return start;
2813 }
2814
2815 static inline
seek_page_size(struct xa_state * xas,struct page * page)2816 unsigned int seek_page_size(struct xa_state *xas, struct page *page)
2817 {
2818 if (xa_is_value(page))
2819 return PAGE_SIZE << xa_get_order(xas->xa, xas->xa_index);
2820 return thp_size(page);
2821 }
2822
2823 /**
2824 * mapping_seek_hole_data - Seek for SEEK_DATA / SEEK_HOLE in the page cache.
2825 * @mapping: Address space to search.
2826 * @start: First byte to consider.
2827 * @end: Limit of search (exclusive).
2828 * @whence: Either SEEK_HOLE or SEEK_DATA.
2829 *
2830 * If the page cache knows which blocks contain holes and which blocks
2831 * contain data, your filesystem can use this function to implement
2832 * SEEK_HOLE and SEEK_DATA. This is useful for filesystems which are
2833 * entirely memory-based such as tmpfs, and filesystems which support
2834 * unwritten extents.
2835 *
2836 * Return: The requested offset on success, or -ENXIO if @whence specifies
2837 * SEEK_DATA and there is no data after @start. There is an implicit hole
2838 * after @end - 1, so SEEK_HOLE returns @end if all the bytes between @start
2839 * and @end contain data.
2840 */
mapping_seek_hole_data(struct address_space * mapping,loff_t start,loff_t end,int whence)2841 loff_t mapping_seek_hole_data(struct address_space *mapping, loff_t start,
2842 loff_t end, int whence)
2843 {
2844 XA_STATE(xas, &mapping->i_pages, start >> PAGE_SHIFT);
2845 pgoff_t max = (end - 1) >> PAGE_SHIFT;
2846 bool seek_data = (whence == SEEK_DATA);
2847 struct page *page;
2848
2849 if (end <= start)
2850 return -ENXIO;
2851
2852 rcu_read_lock();
2853 while ((page = find_get_entry(&xas, max, XA_PRESENT))) {
2854 loff_t pos = (u64)xas.xa_index << PAGE_SHIFT;
2855 unsigned int seek_size;
2856
2857 if (start < pos) {
2858 if (!seek_data)
2859 goto unlock;
2860 start = pos;
2861 }
2862
2863 seek_size = seek_page_size(&xas, page);
2864 pos = round_up(pos + 1, seek_size);
2865 start = page_seek_hole_data(&xas, mapping, page, start, pos,
2866 seek_data);
2867 if (start < pos)
2868 goto unlock;
2869 if (start >= end)
2870 break;
2871 if (seek_size > PAGE_SIZE)
2872 xas_set(&xas, pos >> PAGE_SHIFT);
2873 if (!xa_is_value(page))
2874 put_page(page);
2875 }
2876 if (seek_data)
2877 start = -ENXIO;
2878 unlock:
2879 rcu_read_unlock();
2880 if (page && !xa_is_value(page))
2881 put_page(page);
2882 if (start > end)
2883 return end;
2884 return start;
2885 }
2886
2887 #ifdef CONFIG_MMU
2888 #define MMAP_LOTSAMISS (100)
2889 /*
2890 * lock_page_maybe_drop_mmap - lock the page, possibly dropping the mmap_lock
2891 * @vmf - the vm_fault for this fault.
2892 * @page - the page to lock.
2893 * @fpin - the pointer to the file we may pin (or is already pinned).
2894 *
2895 * This works similar to lock_page_or_retry in that it can drop the mmap_lock.
2896 * It differs in that it actually returns the page locked if it returns 1 and 0
2897 * if it couldn't lock the page. If we did have to drop the mmap_lock then fpin
2898 * will point to the pinned file and needs to be fput()'ed at a later point.
2899 */
lock_page_maybe_drop_mmap(struct vm_fault * vmf,struct page * page,struct file ** fpin)2900 static int lock_page_maybe_drop_mmap(struct vm_fault *vmf, struct page *page,
2901 struct file **fpin)
2902 {
2903 if (trylock_page(page))
2904 return 1;
2905
2906 /*
2907 * NOTE! This will make us return with VM_FAULT_RETRY, but with
2908 * the mmap_lock still held. That's how FAULT_FLAG_RETRY_NOWAIT
2909 * is supposed to work. We have way too many special cases..
2910 */
2911 if (vmf->flags & FAULT_FLAG_RETRY_NOWAIT)
2912 return 0;
2913
2914 *fpin = maybe_unlock_mmap_for_io(vmf, *fpin);
2915 if (vmf->flags & FAULT_FLAG_KILLABLE) {
2916 if (__lock_page_killable(page)) {
2917 /*
2918 * We didn't have the right flags to drop the mmap_lock,
2919 * but all fault_handlers only check for fatal signals
2920 * if we return VM_FAULT_RETRY, so we need to drop the
2921 * mmap_lock here and return 0 if we don't have a fpin.
2922 */
2923 if (*fpin == NULL)
2924 mmap_read_unlock(vmf->vma->vm_mm);
2925 return 0;
2926 }
2927 } else
2928 __lock_page(page);
2929 return 1;
2930 }
2931
2932
2933 /*
2934 * Synchronous readahead happens when we don't even find a page in the page
2935 * cache at all. We don't want to perform IO under the mmap sem, so if we have
2936 * to drop the mmap sem we return the file that was pinned in order for us to do
2937 * that. If we didn't pin a file then we return NULL. The file that is
2938 * returned needs to be fput()'ed when we're done with it.
2939 */
do_sync_mmap_readahead(struct vm_fault * vmf)2940 static struct file *do_sync_mmap_readahead(struct vm_fault *vmf)
2941 {
2942 struct file *file = vmf->vma->vm_file;
2943 struct file_ra_state *ra = &file->f_ra;
2944 struct address_space *mapping = file->f_mapping;
2945 DEFINE_READAHEAD(ractl, file, ra, mapping, vmf->pgoff);
2946 struct file *fpin = NULL;
2947 unsigned int mmap_miss;
2948
2949 /* If we don't want any read-ahead, don't bother */
2950 if (vmf->vma->vm_flags & VM_RAND_READ)
2951 return fpin;
2952 if (!ra->ra_pages)
2953 return fpin;
2954
2955 if (vmf->vma->vm_flags & VM_SEQ_READ) {
2956 fpin = maybe_unlock_mmap_for_io(vmf, fpin);
2957 page_cache_sync_ra(&ractl, ra->ra_pages);
2958 return fpin;
2959 }
2960
2961 /* Avoid banging the cache line if not needed */
2962 mmap_miss = READ_ONCE(ra->mmap_miss);
2963 if (mmap_miss < MMAP_LOTSAMISS * 10)
2964 WRITE_ONCE(ra->mmap_miss, ++mmap_miss);
2965
2966 /*
2967 * Do we miss much more than hit in this file? If so,
2968 * stop bothering with read-ahead. It will only hurt.
2969 */
2970 if (mmap_miss > MMAP_LOTSAMISS)
2971 return fpin;
2972
2973 /*
2974 * mmap read-around
2975 */
2976 fpin = maybe_unlock_mmap_for_io(vmf, fpin);
2977 ra->start = max_t(long, 0, vmf->pgoff - ra->ra_pages / 2);
2978 ra->size = ra->ra_pages;
2979 ra->async_size = ra->ra_pages / 4;
2980 ractl._index = ra->start;
2981 do_page_cache_ra(&ractl, ra->size, ra->async_size);
2982 return fpin;
2983 }
2984
2985 /*
2986 * Asynchronous readahead happens when we find the page and PG_readahead,
2987 * so we want to possibly extend the readahead further. We return the file that
2988 * was pinned if we have to drop the mmap_lock in order to do IO.
2989 */
do_async_mmap_readahead(struct vm_fault * vmf,struct page * page)2990 static struct file *do_async_mmap_readahead(struct vm_fault *vmf,
2991 struct page *page)
2992 {
2993 struct file *file = vmf->vma->vm_file;
2994 struct file_ra_state *ra = &file->f_ra;
2995 struct address_space *mapping = file->f_mapping;
2996 struct file *fpin = NULL;
2997 unsigned int mmap_miss;
2998 pgoff_t offset = vmf->pgoff;
2999
3000 /* If we don't want any read-ahead, don't bother */
3001 if (vmf->vma->vm_flags & VM_RAND_READ || !ra->ra_pages)
3002 return fpin;
3003 mmap_miss = READ_ONCE(ra->mmap_miss);
3004 if (mmap_miss)
3005 WRITE_ONCE(ra->mmap_miss, --mmap_miss);
3006 if (PageReadahead(page)) {
3007 fpin = maybe_unlock_mmap_for_io(vmf, fpin);
3008 page_cache_async_readahead(mapping, ra, file,
3009 page, offset, ra->ra_pages);
3010 }
3011 return fpin;
3012 }
3013
3014 /**
3015 * filemap_fault - read in file data for page fault handling
3016 * @vmf: struct vm_fault containing details of the fault
3017 *
3018 * filemap_fault() is invoked via the vma operations vector for a
3019 * mapped memory region to read in file data during a page fault.
3020 *
3021 * The goto's are kind of ugly, but this streamlines the normal case of having
3022 * it in the page cache, and handles the special cases reasonably without
3023 * having a lot of duplicated code.
3024 *
3025 * vma->vm_mm->mmap_lock must be held on entry.
3026 *
3027 * If our return value has VM_FAULT_RETRY set, it's because the mmap_lock
3028 * may be dropped before doing I/O or by lock_page_maybe_drop_mmap().
3029 *
3030 * If our return value does not have VM_FAULT_RETRY set, the mmap_lock
3031 * has not been released.
3032 *
3033 * We never return with VM_FAULT_RETRY and a bit from VM_FAULT_ERROR set.
3034 *
3035 * Return: bitwise-OR of %VM_FAULT_ codes.
3036 */
filemap_fault(struct vm_fault * vmf)3037 vm_fault_t filemap_fault(struct vm_fault *vmf)
3038 {
3039 int error;
3040 struct file *file = vmf->vma->vm_file;
3041 struct file *fpin = NULL;
3042 struct address_space *mapping = file->f_mapping;
3043 struct inode *inode = mapping->host;
3044 pgoff_t offset = vmf->pgoff;
3045 pgoff_t max_off;
3046 struct page *page;
3047 vm_fault_t ret = 0;
3048 bool mapping_locked = false;
3049
3050 max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
3051 if (unlikely(offset >= max_off))
3052 return VM_FAULT_SIGBUS;
3053
3054 /*
3055 * Do we have something in the page cache already?
3056 */
3057 page = find_get_page(mapping, offset);
3058 if (likely(page)) {
3059 /*
3060 * We found the page, so try async readahead before waiting for
3061 * the lock.
3062 */
3063 if (!(vmf->flags & FAULT_FLAG_TRIED))
3064 fpin = do_async_mmap_readahead(vmf, page);
3065 if (unlikely(!PageUptodate(page))) {
3066 filemap_invalidate_lock_shared(mapping);
3067 mapping_locked = true;
3068 }
3069 } else {
3070 /* No page in the page cache at all */
3071 count_vm_event(PGMAJFAULT);
3072 count_memcg_event_mm(vmf->vma->vm_mm, PGMAJFAULT);
3073 ret = VM_FAULT_MAJOR;
3074 fpin = do_sync_mmap_readahead(vmf);
3075 retry_find:
3076 /*
3077 * See comment in filemap_create_page() why we need
3078 * invalidate_lock
3079 */
3080 if (!mapping_locked) {
3081 filemap_invalidate_lock_shared(mapping);
3082 mapping_locked = true;
3083 }
3084 page = pagecache_get_page(mapping, offset,
3085 FGP_CREAT|FGP_FOR_MMAP,
3086 vmf->gfp_mask);
3087 if (!page) {
3088 if (fpin)
3089 goto out_retry;
3090 filemap_invalidate_unlock_shared(mapping);
3091 return VM_FAULT_OOM;
3092 }
3093 }
3094
3095 if (!lock_page_maybe_drop_mmap(vmf, page, &fpin))
3096 goto out_retry;
3097
3098 /* Did it get truncated? */
3099 if (unlikely(compound_head(page)->mapping != mapping)) {
3100 unlock_page(page);
3101 put_page(page);
3102 goto retry_find;
3103 }
3104 VM_BUG_ON_PAGE(page_to_pgoff(page) != offset, page);
3105
3106 /*
3107 * We have a locked page in the page cache, now we need to check
3108 * that it's up-to-date. If not, it is going to be due to an error.
3109 */
3110 if (unlikely(!PageUptodate(page))) {
3111 /*
3112 * The page was in cache and uptodate and now it is not.
3113 * Strange but possible since we didn't hold the page lock all
3114 * the time. Let's drop everything get the invalidate lock and
3115 * try again.
3116 */
3117 if (!mapping_locked) {
3118 unlock_page(page);
3119 put_page(page);
3120 goto retry_find;
3121 }
3122 goto page_not_uptodate;
3123 }
3124
3125 /*
3126 * We've made it this far and we had to drop our mmap_lock, now is the
3127 * time to return to the upper layer and have it re-find the vma and
3128 * redo the fault.
3129 */
3130 if (fpin) {
3131 unlock_page(page);
3132 goto out_retry;
3133 }
3134 if (mapping_locked)
3135 filemap_invalidate_unlock_shared(mapping);
3136
3137 /*
3138 * Found the page and have a reference on it.
3139 * We must recheck i_size under page lock.
3140 */
3141 max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
3142 if (unlikely(offset >= max_off)) {
3143 unlock_page(page);
3144 put_page(page);
3145 return VM_FAULT_SIGBUS;
3146 }
3147
3148 vmf->page = page;
3149 return ret | VM_FAULT_LOCKED;
3150
3151 page_not_uptodate:
3152 /*
3153 * Umm, take care of errors if the page isn't up-to-date.
3154 * Try to re-read it _once_. We do this synchronously,
3155 * because there really aren't any performance issues here
3156 * and we need to check for errors.
3157 */
3158 fpin = maybe_unlock_mmap_for_io(vmf, fpin);
3159 error = filemap_read_page(file, mapping, page);
3160 if (fpin)
3161 goto out_retry;
3162 put_page(page);
3163
3164 if (!error || error == AOP_TRUNCATED_PAGE)
3165 goto retry_find;
3166 filemap_invalidate_unlock_shared(mapping);
3167
3168 return VM_FAULT_SIGBUS;
3169
3170 out_retry:
3171 /*
3172 * We dropped the mmap_lock, we need to return to the fault handler to
3173 * re-find the vma and come back and find our hopefully still populated
3174 * page.
3175 */
3176 if (page)
3177 put_page(page);
3178 if (mapping_locked)
3179 filemap_invalidate_unlock_shared(mapping);
3180 if (fpin)
3181 fput(fpin);
3182 return ret | VM_FAULT_RETRY;
3183 }
3184 EXPORT_SYMBOL(filemap_fault);
3185
filemap_map_pmd(struct vm_fault * vmf,struct page * page)3186 static bool filemap_map_pmd(struct vm_fault *vmf, struct page *page)
3187 {
3188 struct mm_struct *mm = vmf->vma->vm_mm;
3189
3190 /* Huge page is mapped? No need to proceed. */
3191 if (pmd_trans_huge(*vmf->pmd)) {
3192 unlock_page(page);
3193 put_page(page);
3194 return true;
3195 }
3196
3197 if (pmd_none(*vmf->pmd) && PageTransHuge(page)) {
3198 vm_fault_t ret = do_set_pmd(vmf, page);
3199 if (!ret) {
3200 /* The page is mapped successfully, reference consumed. */
3201 unlock_page(page);
3202 return true;
3203 }
3204 }
3205
3206 if (pmd_none(*vmf->pmd)) {
3207 vmf->ptl = pmd_lock(mm, vmf->pmd);
3208 if (likely(pmd_none(*vmf->pmd))) {
3209 mm_inc_nr_ptes(mm);
3210 pmd_populate(mm, vmf->pmd, vmf->prealloc_pte);
3211 vmf->prealloc_pte = NULL;
3212 }
3213 spin_unlock(vmf->ptl);
3214 }
3215
3216 /* See comment in handle_pte_fault() */
3217 if (pmd_devmap_trans_unstable(vmf->pmd)) {
3218 unlock_page(page);
3219 put_page(page);
3220 return true;
3221 }
3222
3223 return false;
3224 }
3225
next_uptodate_page(struct page * page,struct address_space * mapping,struct xa_state * xas,pgoff_t end_pgoff)3226 static struct page *next_uptodate_page(struct page *page,
3227 struct address_space *mapping,
3228 struct xa_state *xas, pgoff_t end_pgoff)
3229 {
3230 unsigned long max_idx;
3231
3232 do {
3233 if (!page)
3234 return NULL;
3235 if (xas_retry(xas, page))
3236 continue;
3237 if (xa_is_value(page))
3238 continue;
3239 if (PageLocked(page))
3240 continue;
3241 if (!page_cache_get_speculative(page))
3242 continue;
3243 /* Has the page moved or been split? */
3244 if (unlikely(page != xas_reload(xas)))
3245 goto skip;
3246 if (!PageUptodate(page) || PageReadahead(page))
3247 goto skip;
3248 if (PageHWPoison(page))
3249 goto skip;
3250 if (!trylock_page(page))
3251 goto skip;
3252 if (page->mapping != mapping)
3253 goto unlock;
3254 if (!PageUptodate(page))
3255 goto unlock;
3256 max_idx = DIV_ROUND_UP(i_size_read(mapping->host), PAGE_SIZE);
3257 if (xas->xa_index >= max_idx)
3258 goto unlock;
3259 return page;
3260 unlock:
3261 unlock_page(page);
3262 skip:
3263 put_page(page);
3264 } while ((page = xas_next_entry(xas, end_pgoff)) != NULL);
3265
3266 return NULL;
3267 }
3268
first_map_page(struct address_space * mapping,struct xa_state * xas,pgoff_t end_pgoff)3269 static inline struct page *first_map_page(struct address_space *mapping,
3270 struct xa_state *xas,
3271 pgoff_t end_pgoff)
3272 {
3273 return next_uptodate_page(xas_find(xas, end_pgoff),
3274 mapping, xas, end_pgoff);
3275 }
3276
next_map_page(struct address_space * mapping,struct xa_state * xas,pgoff_t end_pgoff)3277 static inline struct page *next_map_page(struct address_space *mapping,
3278 struct xa_state *xas,
3279 pgoff_t end_pgoff)
3280 {
3281 return next_uptodate_page(xas_next_entry(xas, end_pgoff),
3282 mapping, xas, end_pgoff);
3283 }
3284
filemap_map_pages(struct vm_fault * vmf,pgoff_t start_pgoff,pgoff_t end_pgoff)3285 vm_fault_t filemap_map_pages(struct vm_fault *vmf,
3286 pgoff_t start_pgoff, pgoff_t end_pgoff)
3287 {
3288 struct vm_area_struct *vma = vmf->vma;
3289 struct file *file = vma->vm_file;
3290 struct address_space *mapping = file->f_mapping;
3291 pgoff_t last_pgoff = start_pgoff;
3292 unsigned long addr;
3293 XA_STATE(xas, &mapping->i_pages, start_pgoff);
3294 struct page *head, *page;
3295 unsigned int mmap_miss = READ_ONCE(file->f_ra.mmap_miss);
3296 vm_fault_t ret = 0;
3297
3298 rcu_read_lock();
3299 head = first_map_page(mapping, &xas, end_pgoff);
3300 if (!head)
3301 goto out;
3302
3303 if (filemap_map_pmd(vmf, head)) {
3304 ret = VM_FAULT_NOPAGE;
3305 goto out;
3306 }
3307
3308 addr = vma->vm_start + ((start_pgoff - vma->vm_pgoff) << PAGE_SHIFT);
3309 vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd, addr, &vmf->ptl);
3310 do {
3311 page = find_subpage(head, xas.xa_index);
3312 if (PageHWPoison(page))
3313 goto unlock;
3314
3315 if (mmap_miss > 0)
3316 mmap_miss--;
3317
3318 addr += (xas.xa_index - last_pgoff) << PAGE_SHIFT;
3319 vmf->pte += xas.xa_index - last_pgoff;
3320 last_pgoff = xas.xa_index;
3321
3322 if (!pte_none(*vmf->pte))
3323 goto unlock;
3324
3325 /* We're about to handle the fault */
3326 if (vmf->address == addr)
3327 ret = VM_FAULT_NOPAGE;
3328
3329 do_set_pte(vmf, page, addr);
3330 /* no need to invalidate: a not-present page won't be cached */
3331 update_mmu_cache(vma, addr, vmf->pte);
3332 unlock_page(head);
3333 continue;
3334 unlock:
3335 unlock_page(head);
3336 put_page(head);
3337 } while ((head = next_map_page(mapping, &xas, end_pgoff)) != NULL);
3338 pte_unmap_unlock(vmf->pte, vmf->ptl);
3339 out:
3340 rcu_read_unlock();
3341 WRITE_ONCE(file->f_ra.mmap_miss, mmap_miss);
3342 return ret;
3343 }
3344 EXPORT_SYMBOL(filemap_map_pages);
3345
filemap_page_mkwrite(struct vm_fault * vmf)3346 vm_fault_t filemap_page_mkwrite(struct vm_fault *vmf)
3347 {
3348 struct address_space *mapping = vmf->vma->vm_file->f_mapping;
3349 struct page *page = vmf->page;
3350 vm_fault_t ret = VM_FAULT_LOCKED;
3351
3352 sb_start_pagefault(mapping->host->i_sb);
3353 file_update_time(vmf->vma->vm_file);
3354 lock_page(page);
3355 if (page->mapping != mapping) {
3356 unlock_page(page);
3357 ret = VM_FAULT_NOPAGE;
3358 goto out;
3359 }
3360 /*
3361 * We mark the page dirty already here so that when freeze is in
3362 * progress, we are guaranteed that writeback during freezing will
3363 * see the dirty page and writeprotect it again.
3364 */
3365 set_page_dirty(page);
3366 wait_for_stable_page(page);
3367 out:
3368 sb_end_pagefault(mapping->host->i_sb);
3369 return ret;
3370 }
3371
3372 const struct vm_operations_struct generic_file_vm_ops = {
3373 .fault = filemap_fault,
3374 .map_pages = filemap_map_pages,
3375 .page_mkwrite = filemap_page_mkwrite,
3376 };
3377
3378 /* This is used for a general mmap of a disk file */
3379
generic_file_mmap(struct file * file,struct vm_area_struct * vma)3380 int generic_file_mmap(struct file *file, struct vm_area_struct *vma)
3381 {
3382 struct address_space *mapping = file->f_mapping;
3383
3384 if (!mapping->a_ops->readpage)
3385 return -ENOEXEC;
3386 file_accessed(file);
3387 vma->vm_ops = &generic_file_vm_ops;
3388 return 0;
3389 }
3390
3391 /*
3392 * This is for filesystems which do not implement ->writepage.
3393 */
generic_file_readonly_mmap(struct file * file,struct vm_area_struct * vma)3394 int generic_file_readonly_mmap(struct file *file, struct vm_area_struct *vma)
3395 {
3396 if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE))
3397 return -EINVAL;
3398 return generic_file_mmap(file, vma);
3399 }
3400 #else
filemap_page_mkwrite(struct vm_fault * vmf)3401 vm_fault_t filemap_page_mkwrite(struct vm_fault *vmf)
3402 {
3403 return VM_FAULT_SIGBUS;
3404 }
generic_file_mmap(struct file * file,struct vm_area_struct * vma)3405 int generic_file_mmap(struct file *file, struct vm_area_struct *vma)
3406 {
3407 return -ENOSYS;
3408 }
generic_file_readonly_mmap(struct file * file,struct vm_area_struct * vma)3409 int generic_file_readonly_mmap(struct file *file, struct vm_area_struct *vma)
3410 {
3411 return -ENOSYS;
3412 }
3413 #endif /* CONFIG_MMU */
3414
3415 EXPORT_SYMBOL(filemap_page_mkwrite);
3416 EXPORT_SYMBOL(generic_file_mmap);
3417 EXPORT_SYMBOL(generic_file_readonly_mmap);
3418
wait_on_page_read(struct page * page)3419 static struct page *wait_on_page_read(struct page *page)
3420 {
3421 if (!IS_ERR(page)) {
3422 wait_on_page_locked(page);
3423 if (!PageUptodate(page)) {
3424 put_page(page);
3425 page = ERR_PTR(-EIO);
3426 }
3427 }
3428 return page;
3429 }
3430
do_read_cache_page(struct address_space * mapping,pgoff_t index,int (* filler)(void *,struct page *),void * data,gfp_t gfp)3431 static struct page *do_read_cache_page(struct address_space *mapping,
3432 pgoff_t index,
3433 int (*filler)(void *, struct page *),
3434 void *data,
3435 gfp_t gfp)
3436 {
3437 struct page *page;
3438 int err;
3439 repeat:
3440 page = find_get_page(mapping, index);
3441 if (!page) {
3442 page = __page_cache_alloc(gfp);
3443 if (!page)
3444 return ERR_PTR(-ENOMEM);
3445 err = add_to_page_cache_lru(page, mapping, index, gfp);
3446 if (unlikely(err)) {
3447 put_page(page);
3448 if (err == -EEXIST)
3449 goto repeat;
3450 /* Presumably ENOMEM for xarray node */
3451 return ERR_PTR(err);
3452 }
3453
3454 filler:
3455 if (filler)
3456 err = filler(data, page);
3457 else
3458 err = mapping->a_ops->readpage(data, page);
3459
3460 if (err < 0) {
3461 put_page(page);
3462 return ERR_PTR(err);
3463 }
3464
3465 page = wait_on_page_read(page);
3466 if (IS_ERR(page))
3467 return page;
3468 goto out;
3469 }
3470 if (PageUptodate(page))
3471 goto out;
3472
3473 /*
3474 * Page is not up to date and may be locked due to one of the following
3475 * case a: Page is being filled and the page lock is held
3476 * case b: Read/write error clearing the page uptodate status
3477 * case c: Truncation in progress (page locked)
3478 * case d: Reclaim in progress
3479 *
3480 * Case a, the page will be up to date when the page is unlocked.
3481 * There is no need to serialise on the page lock here as the page
3482 * is pinned so the lock gives no additional protection. Even if the
3483 * page is truncated, the data is still valid if PageUptodate as
3484 * it's a race vs truncate race.
3485 * Case b, the page will not be up to date
3486 * Case c, the page may be truncated but in itself, the data may still
3487 * be valid after IO completes as it's a read vs truncate race. The
3488 * operation must restart if the page is not uptodate on unlock but
3489 * otherwise serialising on page lock to stabilise the mapping gives
3490 * no additional guarantees to the caller as the page lock is
3491 * released before return.
3492 * Case d, similar to truncation. If reclaim holds the page lock, it
3493 * will be a race with remove_mapping that determines if the mapping
3494 * is valid on unlock but otherwise the data is valid and there is
3495 * no need to serialise with page lock.
3496 *
3497 * As the page lock gives no additional guarantee, we optimistically
3498 * wait on the page to be unlocked and check if it's up to date and
3499 * use the page if it is. Otherwise, the page lock is required to
3500 * distinguish between the different cases. The motivation is that we
3501 * avoid spurious serialisations and wakeups when multiple processes
3502 * wait on the same page for IO to complete.
3503 */
3504 wait_on_page_locked(page);
3505 if (PageUptodate(page))
3506 goto out;
3507
3508 /* Distinguish between all the cases under the safety of the lock */
3509 lock_page(page);
3510
3511 /* Case c or d, restart the operation */
3512 if (!page->mapping) {
3513 unlock_page(page);
3514 put_page(page);
3515 goto repeat;
3516 }
3517
3518 /* Someone else locked and filled the page in a very small window */
3519 if (PageUptodate(page)) {
3520 unlock_page(page);
3521 goto out;
3522 }
3523
3524 /*
3525 * A previous I/O error may have been due to temporary
3526 * failures.
3527 * Clear page error before actual read, PG_error will be
3528 * set again if read page fails.
3529 */
3530 ClearPageError(page);
3531 goto filler;
3532
3533 out:
3534 mark_page_accessed(page);
3535 return page;
3536 }
3537
3538 /**
3539 * read_cache_page - read into page cache, fill it if needed
3540 * @mapping: the page's address_space
3541 * @index: the page index
3542 * @filler: function to perform the read
3543 * @data: first arg to filler(data, page) function, often left as NULL
3544 *
3545 * Read into the page cache. If a page already exists, and PageUptodate() is
3546 * not set, try to fill the page and wait for it to become unlocked.
3547 *
3548 * If the page does not get brought uptodate, return -EIO.
3549 *
3550 * The function expects mapping->invalidate_lock to be already held.
3551 *
3552 * Return: up to date page on success, ERR_PTR() on failure.
3553 */
read_cache_page(struct address_space * mapping,pgoff_t index,int (* filler)(void *,struct page *),void * data)3554 struct page *read_cache_page(struct address_space *mapping,
3555 pgoff_t index,
3556 int (*filler)(void *, struct page *),
3557 void *data)
3558 {
3559 return do_read_cache_page(mapping, index, filler, data,
3560 mapping_gfp_mask(mapping));
3561 }
3562 EXPORT_SYMBOL(read_cache_page);
3563
3564 /**
3565 * read_cache_page_gfp - read into page cache, using specified page allocation flags.
3566 * @mapping: the page's address_space
3567 * @index: the page index
3568 * @gfp: the page allocator flags to use if allocating
3569 *
3570 * This is the same as "read_mapping_page(mapping, index, NULL)", but with
3571 * any new page allocations done using the specified allocation flags.
3572 *
3573 * If the page does not get brought uptodate, return -EIO.
3574 *
3575 * The function expects mapping->invalidate_lock to be already held.
3576 *
3577 * Return: up to date page on success, ERR_PTR() on failure.
3578 */
read_cache_page_gfp(struct address_space * mapping,pgoff_t index,gfp_t gfp)3579 struct page *read_cache_page_gfp(struct address_space *mapping,
3580 pgoff_t index,
3581 gfp_t gfp)
3582 {
3583 return do_read_cache_page(mapping, index, NULL, NULL, gfp);
3584 }
3585 EXPORT_SYMBOL(read_cache_page_gfp);
3586
pagecache_write_begin(struct file * file,struct address_space * mapping,loff_t pos,unsigned len,unsigned flags,struct page ** pagep,void ** fsdata)3587 int pagecache_write_begin(struct file *file, struct address_space *mapping,
3588 loff_t pos, unsigned len, unsigned flags,
3589 struct page **pagep, void **fsdata)
3590 {
3591 const struct address_space_operations *aops = mapping->a_ops;
3592
3593 return aops->write_begin(file, mapping, pos, len, flags,
3594 pagep, fsdata);
3595 }
3596 EXPORT_SYMBOL(pagecache_write_begin);
3597
pagecache_write_end(struct file * file,struct address_space * mapping,loff_t pos,unsigned len,unsigned copied,struct page * page,void * fsdata)3598 int pagecache_write_end(struct file *file, struct address_space *mapping,
3599 loff_t pos, unsigned len, unsigned copied,
3600 struct page *page, void *fsdata)
3601 {
3602 const struct address_space_operations *aops = mapping->a_ops;
3603
3604 return aops->write_end(file, mapping, pos, len, copied, page, fsdata);
3605 }
3606 EXPORT_SYMBOL(pagecache_write_end);
3607
3608 /*
3609 * Warn about a page cache invalidation failure during a direct I/O write.
3610 */
dio_warn_stale_pagecache(struct file * filp)3611 void dio_warn_stale_pagecache(struct file *filp)
3612 {
3613 static DEFINE_RATELIMIT_STATE(_rs, 86400 * HZ, DEFAULT_RATELIMIT_BURST);
3614 char pathname[128];
3615 char *path;
3616
3617 errseq_set(&filp->f_mapping->wb_err, -EIO);
3618 if (__ratelimit(&_rs)) {
3619 path = file_path(filp, pathname, sizeof(pathname));
3620 if (IS_ERR(path))
3621 path = "(unknown)";
3622 pr_crit("Page cache invalidation failure on direct I/O. Possible data corruption due to collision with buffered I/O!\n");
3623 pr_crit("File: %s PID: %d Comm: %.20s\n", path, current->pid,
3624 current->comm);
3625 }
3626 }
3627
3628 ssize_t
generic_file_direct_write(struct kiocb * iocb,struct iov_iter * from)3629 generic_file_direct_write(struct kiocb *iocb, struct iov_iter *from)
3630 {
3631 struct file *file = iocb->ki_filp;
3632 struct address_space *mapping = file->f_mapping;
3633 struct inode *inode = mapping->host;
3634 loff_t pos = iocb->ki_pos;
3635 ssize_t written;
3636 size_t write_len;
3637 pgoff_t end;
3638
3639 write_len = iov_iter_count(from);
3640 end = (pos + write_len - 1) >> PAGE_SHIFT;
3641
3642 if (iocb->ki_flags & IOCB_NOWAIT) {
3643 /* If there are pages to writeback, return */
3644 if (filemap_range_has_page(file->f_mapping, pos,
3645 pos + write_len - 1))
3646 return -EAGAIN;
3647 } else {
3648 written = filemap_write_and_wait_range(mapping, pos,
3649 pos + write_len - 1);
3650 if (written)
3651 goto out;
3652 }
3653
3654 /*
3655 * After a write we want buffered reads to be sure to go to disk to get
3656 * the new data. We invalidate clean cached page from the region we're
3657 * about to write. We do this *before* the write so that we can return
3658 * without clobbering -EIOCBQUEUED from ->direct_IO().
3659 */
3660 written = invalidate_inode_pages2_range(mapping,
3661 pos >> PAGE_SHIFT, end);
3662 /*
3663 * If a page can not be invalidated, return 0 to fall back
3664 * to buffered write.
3665 */
3666 if (written) {
3667 if (written == -EBUSY)
3668 return 0;
3669 goto out;
3670 }
3671
3672 written = mapping->a_ops->direct_IO(iocb, from);
3673
3674 /*
3675 * Finally, try again to invalidate clean pages which might have been
3676 * cached by non-direct readahead, or faulted in by get_user_pages()
3677 * if the source of the write was an mmap'ed region of the file
3678 * we're writing. Either one is a pretty crazy thing to do,
3679 * so we don't support it 100%. If this invalidation
3680 * fails, tough, the write still worked...
3681 *
3682 * Most of the time we do not need this since dio_complete() will do
3683 * the invalidation for us. However there are some file systems that
3684 * do not end up with dio_complete() being called, so let's not break
3685 * them by removing it completely.
3686 *
3687 * Noticeable example is a blkdev_direct_IO().
3688 *
3689 * Skip invalidation for async writes or if mapping has no pages.
3690 */
3691 if (written > 0 && mapping->nrpages &&
3692 invalidate_inode_pages2_range(mapping, pos >> PAGE_SHIFT, end))
3693 dio_warn_stale_pagecache(file);
3694
3695 if (written > 0) {
3696 pos += written;
3697 write_len -= written;
3698 if (pos > i_size_read(inode) && !S_ISBLK(inode->i_mode)) {
3699 i_size_write(inode, pos);
3700 mark_inode_dirty(inode);
3701 }
3702 iocb->ki_pos = pos;
3703 }
3704 if (written != -EIOCBQUEUED)
3705 iov_iter_revert(from, write_len - iov_iter_count(from));
3706 out:
3707 return written;
3708 }
3709 EXPORT_SYMBOL(generic_file_direct_write);
3710
3711 /*
3712 * Find or create a page at the given pagecache position. Return the locked
3713 * page. This function is specifically for buffered writes.
3714 */
grab_cache_page_write_begin(struct address_space * mapping,pgoff_t index,unsigned flags)3715 struct page *grab_cache_page_write_begin(struct address_space *mapping,
3716 pgoff_t index, unsigned flags)
3717 {
3718 struct page *page;
3719 int fgp_flags = FGP_LOCK|FGP_WRITE|FGP_CREAT;
3720
3721 if (flags & AOP_FLAG_NOFS)
3722 fgp_flags |= FGP_NOFS;
3723
3724 page = pagecache_get_page(mapping, index, fgp_flags,
3725 mapping_gfp_mask(mapping));
3726 if (page)
3727 wait_for_stable_page(page);
3728
3729 return page;
3730 }
3731 EXPORT_SYMBOL(grab_cache_page_write_begin);
3732
generic_perform_write(struct file * file,struct iov_iter * i,loff_t pos)3733 ssize_t generic_perform_write(struct file *file,
3734 struct iov_iter *i, loff_t pos)
3735 {
3736 struct address_space *mapping = file->f_mapping;
3737 const struct address_space_operations *a_ops = mapping->a_ops;
3738 long status = 0;
3739 ssize_t written = 0;
3740 unsigned int flags = 0;
3741
3742 do {
3743 struct page *page;
3744 unsigned long offset; /* Offset into pagecache page */
3745 unsigned long bytes; /* Bytes to write to page */
3746 size_t copied; /* Bytes copied from user */
3747 void *fsdata;
3748
3749 offset = (pos & (PAGE_SIZE - 1));
3750 bytes = min_t(unsigned long, PAGE_SIZE - offset,
3751 iov_iter_count(i));
3752
3753 again:
3754 /*
3755 * Bring in the user page that we will copy from _first_.
3756 * Otherwise there's a nasty deadlock on copying from the
3757 * same page as we're writing to, without it being marked
3758 * up-to-date.
3759 */
3760 if (unlikely(iov_iter_fault_in_readable(i, bytes))) {
3761 status = -EFAULT;
3762 break;
3763 }
3764
3765 if (fatal_signal_pending(current)) {
3766 status = -EINTR;
3767 break;
3768 }
3769
3770 status = a_ops->write_begin(file, mapping, pos, bytes, flags,
3771 &page, &fsdata);
3772 if (unlikely(status < 0))
3773 break;
3774
3775 if (mapping_writably_mapped(mapping))
3776 flush_dcache_page(page);
3777
3778 copied = copy_page_from_iter_atomic(page, offset, bytes, i);
3779 flush_dcache_page(page);
3780
3781 status = a_ops->write_end(file, mapping, pos, bytes, copied,
3782 page, fsdata);
3783 if (unlikely(status != copied)) {
3784 iov_iter_revert(i, copied - max(status, 0L));
3785 if (unlikely(status < 0))
3786 break;
3787 }
3788 cond_resched();
3789
3790 if (unlikely(status == 0)) {
3791 /*
3792 * A short copy made ->write_end() reject the
3793 * thing entirely. Might be memory poisoning
3794 * halfway through, might be a race with munmap,
3795 * might be severe memory pressure.
3796 */
3797 if (copied)
3798 bytes = copied;
3799 goto again;
3800 }
3801 pos += status;
3802 written += status;
3803
3804 balance_dirty_pages_ratelimited(mapping);
3805 } while (iov_iter_count(i));
3806
3807 return written ? written : status;
3808 }
3809 EXPORT_SYMBOL(generic_perform_write);
3810
3811 /**
3812 * __generic_file_write_iter - write data to a file
3813 * @iocb: IO state structure (file, offset, etc.)
3814 * @from: iov_iter with data to write
3815 *
3816 * This function does all the work needed for actually writing data to a
3817 * file. It does all basic checks, removes SUID from the file, updates
3818 * modification times and calls proper subroutines depending on whether we
3819 * do direct IO or a standard buffered write.
3820 *
3821 * It expects i_rwsem to be grabbed unless we work on a block device or similar
3822 * object which does not need locking at all.
3823 *
3824 * This function does *not* take care of syncing data in case of O_SYNC write.
3825 * A caller has to handle it. This is mainly due to the fact that we want to
3826 * avoid syncing under i_rwsem.
3827 *
3828 * Return:
3829 * * number of bytes written, even for truncated writes
3830 * * negative error code if no data has been written at all
3831 */
__generic_file_write_iter(struct kiocb * iocb,struct iov_iter * from)3832 ssize_t __generic_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
3833 {
3834 struct file *file = iocb->ki_filp;
3835 struct address_space *mapping = file->f_mapping;
3836 struct inode *inode = mapping->host;
3837 ssize_t written = 0;
3838 ssize_t err;
3839 ssize_t status;
3840
3841 /* We can write back this queue in page reclaim */
3842 current->backing_dev_info = inode_to_bdi(inode);
3843 err = file_remove_privs(file);
3844 if (err)
3845 goto out;
3846
3847 err = file_update_time(file);
3848 if (err)
3849 goto out;
3850
3851 if (iocb->ki_flags & IOCB_DIRECT) {
3852 loff_t pos, endbyte;
3853
3854 written = generic_file_direct_write(iocb, from);
3855 /*
3856 * If the write stopped short of completing, fall back to
3857 * buffered writes. Some filesystems do this for writes to
3858 * holes, for example. For DAX files, a buffered write will
3859 * not succeed (even if it did, DAX does not handle dirty
3860 * page-cache pages correctly).
3861 */
3862 if (written < 0 || !iov_iter_count(from) || IS_DAX(inode))
3863 goto out;
3864
3865 status = generic_perform_write(file, from, pos = iocb->ki_pos);
3866 /*
3867 * If generic_perform_write() returned a synchronous error
3868 * then we want to return the number of bytes which were
3869 * direct-written, or the error code if that was zero. Note
3870 * that this differs from normal direct-io semantics, which
3871 * will return -EFOO even if some bytes were written.
3872 */
3873 if (unlikely(status < 0)) {
3874 err = status;
3875 goto out;
3876 }
3877 /*
3878 * We need to ensure that the page cache pages are written to
3879 * disk and invalidated to preserve the expected O_DIRECT
3880 * semantics.
3881 */
3882 endbyte = pos + status - 1;
3883 err = filemap_write_and_wait_range(mapping, pos, endbyte);
3884 if (err == 0) {
3885 iocb->ki_pos = endbyte + 1;
3886 written += status;
3887 invalidate_mapping_pages(mapping,
3888 pos >> PAGE_SHIFT,
3889 endbyte >> PAGE_SHIFT);
3890 } else {
3891 /*
3892 * We don't know how much we wrote, so just return
3893 * the number of bytes which were direct-written
3894 */
3895 }
3896 } else {
3897 written = generic_perform_write(file, from, iocb->ki_pos);
3898 if (likely(written > 0))
3899 iocb->ki_pos += written;
3900 }
3901 out:
3902 current->backing_dev_info = NULL;
3903 return written ? written : err;
3904 }
3905 EXPORT_SYMBOL(__generic_file_write_iter);
3906
3907 /**
3908 * generic_file_write_iter - write data to a file
3909 * @iocb: IO state structure
3910 * @from: iov_iter with data to write
3911 *
3912 * This is a wrapper around __generic_file_write_iter() to be used by most
3913 * filesystems. It takes care of syncing the file in case of O_SYNC file
3914 * and acquires i_rwsem as needed.
3915 * Return:
3916 * * negative error code if no data has been written at all of
3917 * vfs_fsync_range() failed for a synchronous write
3918 * * number of bytes written, even for truncated writes
3919 */
generic_file_write_iter(struct kiocb * iocb,struct iov_iter * from)3920 ssize_t generic_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
3921 {
3922 struct file *file = iocb->ki_filp;
3923 struct inode *inode = file->f_mapping->host;
3924 ssize_t ret;
3925
3926 inode_lock(inode);
3927 ret = generic_write_checks(iocb, from);
3928 if (ret > 0)
3929 ret = __generic_file_write_iter(iocb, from);
3930 inode_unlock(inode);
3931
3932 if (ret > 0)
3933 ret = generic_write_sync(iocb, ret);
3934 return ret;
3935 }
3936 EXPORT_SYMBOL(generic_file_write_iter);
3937
3938 /**
3939 * try_to_release_page() - release old fs-specific metadata on a page
3940 *
3941 * @page: the page which the kernel is trying to free
3942 * @gfp_mask: memory allocation flags (and I/O mode)
3943 *
3944 * The address_space is to try to release any data against the page
3945 * (presumably at page->private).
3946 *
3947 * This may also be called if PG_fscache is set on a page, indicating that the
3948 * page is known to the local caching routines.
3949 *
3950 * The @gfp_mask argument specifies whether I/O may be performed to release
3951 * this page (__GFP_IO), and whether the call may block (__GFP_RECLAIM & __GFP_FS).
3952 *
3953 * Return: %1 if the release was successful, otherwise return zero.
3954 */
try_to_release_page(struct page * page,gfp_t gfp_mask)3955 int try_to_release_page(struct page *page, gfp_t gfp_mask)
3956 {
3957 struct address_space * const mapping = page->mapping;
3958
3959 BUG_ON(!PageLocked(page));
3960 if (PageWriteback(page))
3961 return 0;
3962
3963 if (mapping && mapping->a_ops->releasepage)
3964 return mapping->a_ops->releasepage(page, gfp_mask);
3965 return try_to_free_buffers(page);
3966 }
3967
3968 EXPORT_SYMBOL(try_to_release_page);
3969